View Full Version : Tubb 42 coil spring in 5.56 guns and why it runs almost everything
This posting is two parts. First, why I'm using the Tubb 42 coil spring in everything now, and secondly a bit deeper dive into the physics of what's happening that allow it to work well and why it might be a good choice for several applications. I'll assume you've seen Tubb's promo video (https://youtu.be/8fMVZbrnvu8) on these flat springs comparing them to some mil spec and Sprinco springs. I have no affiliation in any capacity with David Tubb or any reseller of his products, FYI.
I've taken to using the 42 coil Tubb flat spring (his ".308 spring") in just about everything 5.56. I bought it initially to test in my #1 rifle, my DDM4 V11 pro (18" rifle gas), expecting to have to trim it back (to ~36 coils) to get it to function properly. After all, Tubb sells at 36 coil version of this spring he intended for carbine and rifle use in 5.56 guns. Turns out my 18" rifle gas upper loves it with all 42 coils in a carbine lower with an H1. Smooth and reliable. Turn out my 16" middy loves it with the same lower.
And it turns out that it runs great in my two different A5 lowers with either A5H2 or A5H3 buffers with the same uppers. How can the same spring work so well in such different applications? ("working well" here means it provides excellent power to cycle the gun, has a smooth recoil impulse without inducing functional issues or screwing up timing).
As many of you already know, it is a very long spring:
https://i.imgur.com/vy2JoZx.jpg
The question: why does this "too stiff" spring work so well in both carbine and A5 5.56 guns? Some basics about springs will help us understand. A spring works like a coiled torsion bar. You might remember torsion bar suspension from old Mopars in the classic muscle car era. Instead of the spring being coiled up, the torsion bar spring was essentially just twisting a solid steel rod. But if you were to wind this rod around a cylinder, you'd find you had a coiled spring that experienced stresses pretty much the same way. A coil spring works by inducing a twisting force on the wire of the spring.
A longer spring experiences less change in load with distance than the same spring at a shorter length-- this is because the same twist is distributed across a longer run of wire. So if I have two otherwise identical springs-- one 12" long and the other 24" long, we'd find that compressing them the same distance (say, 3.5" or so) would show the shorter spring to get "stiffer" at a much faster rate. In engineering terms, has has a different spring rate (F=kx, force as a function of spring rate and displacement/distance). They have different rates EVEN THOUGH the wire is exactly the same, the diameter is the same, and all other features are the same.
The comically long 42 coil Tubb spring ends up being very linear in force because of its length. This lets you have more force to hold the bolt closed, more force to strip a round from a magazine, and more reserve to cycle the gun but NOT have so much spring force at the rear of the gun that the timing of the rifle is affected and inducing short stroking or having the bolt cycle so fast it outruns the mag springs. It preserves the "dwell" at the rear necessary to let the next round present itself.
The Tubb video shows this rather strikingly. The 36 coil version of the spring has 10.5# bolt closed, 16.3# bolt open. This compares to a new carbine spring at ~8# bolt closed and 16.5# bolt open. The long 42 coil spring has 13# at bolt closed, but still just 16.7# at bolt open. Not even 4# difference between open and closed.
Takeaway: the 42 coil spring has a lower spring rate (change in load with change in distance) even at higher applied force. This is a good thing. We want the rate as flat as possible.
So now for the theory part:
While both buffer weight and spring force resist the rearward travel of the bolt, they do so very differently. The spring directly applies force, regardless how fast the bolt is moving (putting aside spring dynamics for the moment). It resists the bolt based on *position*.
The buffer, on the other hand, can only apply inertial force as a function of bolt acceleration. F=MA. No acceleration on the buffer, no force!
So when we start with higher spring preload holding the bolt closed, we not only gain more time in bolt closed dwell (time for blowdown and extraction), we also make the rifle less sensitive to differences in buffer weight because the bolt isn't moving to the rear as quickly.
If I double the spring force holding the bolt closed, then the initial acceleration of the bolt to the rearward would be cut in half. If the bolt has half the acceleration rearward, then the "apparent weight" of the buffer is less. Let's say for illustrative purposes that in one case, the bolt accelerates rearward at 20g and in the other, it heads rearward at 10g (where "g" is acceleration of gravity at ~ 32.2 ft /sec^2).
In the 20g case, an H buffer that weighs 3.8oz can actually apply a force of (20x3.8 oz=) 76 ounces. An H2 at the same acceleration would appear to apply a force of (~4.6ox x20g=) 92 ounces. This is a difference between buffers of 16 ounces.
But if I slow the bolt down to 10g acceleration, now the apparent forces for the H1 and H2 are 38oz and 46 ounces, respectively, a difference of just 8 ounces.
By some simple math, in order to produce the same retarding force at bolt closed that the Tubb 42 coil spring does (13#), an H2 carbine buffer would have to be accelerating at ~ 45g. Obviously it will only exceed this acceleration value (if it does at all) very briefly because immediately after the gas key disengages the gas tube, the BCG is slowing very quickly.
So why does it work in an A5 setup so well? This goes back to the long length. Being just 3/4" longer, the A5 doesn't drastically change the operating environment of the spring relative to carbine. It will have slightly less force at bolt closed and bolt open, but still quite a bit more than an A2 rifle spring, and also be more linear in terms of spring rate (force gain, if you will). Because it's applying load to the BCG even at zero acceleration, it is making the apparent differences in buffer weights seem less.
If you want more closed bolt dwell time, a stiffer spring is far more effective than a heavier buffer because the latter can only be relevant AFTER the bolt has started moving. By definition, this is after the "dwell" time is over and we've proceeded to unlock and extraction.
This approach -- more spring, more spring linearity, less buffer-- should have a broader operating envelope and provide better margin across loads and also suppressed vs not. My informal testing isn't really scientific, but it strongly suggests this is the case.
Remember, all of the energy available to cycle the gun comes from the spring. A buffer that's too heavy will deprive the spring of its full energy capacity by not compressing it all the way. A buffer that's too light will let the excess energy arrive at the shooter's shoulder when the buffer bottoms out hard in the tube-- it is attempting to deliver more energy than the spring can store.
This is why the big 42 coil spring can allow the same uppers to run great with something as heavy as the 6oz A5h3 all the way down to my 3.8oz H1 carbine setup.
Ejection with all lowers was pretty much the same spot at 4:00 with Geco .223 factory and even my weak 8208XBR hand loads, and it didn't seem to matter which lower or buffer weight was in use. Both carbine and A5 lowers ejected to the same spot and locked back on empty mags.
I point that out not that 4:00 ejection is evidence of perfection. Rather, the *consistent* ejection across buffer weights, across carbine vs A5, across factory load vs weak hand load, appears to confirm that the spring makes the gun much less sensitive and less sensitivity means a broader operating envelope.
This is why I think the 42 coil Tubb spring might be a good choice overall for almost any carbine or A5 setup. It should be kinder to your brass and enhance extraction by giving more closed bolt dwell, give you extra force to strip a round when its more difficult (debris, dirty mag) and overall have more effective operating envelope.
That has been my experience so far, admittedly with only basic function tests with A5 and about two years and ~1000 rounds in a carbine lower with H1. Perhaps a higher volume shooter has more insight? I think a lot of guys using the Tubb springs are using his 36 coil version and missing out on the virtues of the 42 coil one.
H
I've been using the 42 coil spring in a suppressed mid-length for a while. While this particular setup doesn't get shot too often, I've been very happy with it. I tried it at the suggestion of someone here on the forum, and compared it to the Springco Green spring. I found the Tubb spring had less dot movement while functioning as well as the Sprinco. Prior to that, the Springco has always been my go to.
If anyone has experience tuning motorcycle racing suspension, the analogy here is: lower spring rate, but more preload. Kinda like A5 vs carbine.
I’ve also been experimenting with Tubb springs (again), but the 556 one. I’ve been measuring it in comparison to others. I like it in the A5, but it seems a little much in carbine RE’s. Too much preload.
Little known thing about springs is that removing coils increases, not decreases, spring rate. Given identical space to work with, that means the shorter spring (of same material and diameters, etc) has less preload, but higher rate. Something to consider if you are burning brain-calories comparing carbine to rifle to A5 REs.
Its the only non-Colt spring I like, really. I tried to like the lighter Sprincos, but they rust too fast. I wouldn’t swap a working Colt spring for one.
I've never had a chrome silicone spring rust, but I lightly lube all my springs, so that may be why. That said, I found the Sprinco blue to be unnecessarily heavy for my middys.
Have a Tubb flat wire in my 308, and I think I'm going to try it in my 5.56s and see if I like it. The OP is compelling, and I'll probably order one for each of them.
I think the spring and buffer stuff is interesting but I have a 6920 that’s 13 years old and is functionally stock and has digested untold amounts of ammo, everything from Wolff steel case and PMC Bronze to hot IMI that blew primers.
I think the spring and buffer stuff is interesting but I have a 6920 that’s 13 years old and is functionally stock and has digested untold amounts of ammo, everything from Wolff steel case and PMC Bronze to hot IMI that blew primers.This isn't primarily about reliability, but about flatter shooting whilst maintaining reliability.
One thing interesting about 42 coil Tubb is no matter how slowly I ride the charging handle forward, it has the power to strip and chamber a round cleanly with my carbine lower. Even a full 40rd PMAG or a full ASC with rough lips. That might be a potential reliability enhancement or nothing at all.
Reliability overall is easy to achieve. Just use mil spec parts and change as frequently as needed. The appeal of the 42 coil is that it might be something of a free lunch— less recoil without a reliability penalty or margin reduction.
If anyone has experience tuning motorcycle racing suspension, the analogy here is: lower spring rate, but more preload. Kinda like A5 vs carbine.
I’ve also been experimenting with Tubb springs (again), but the 556 one. I’ve been measuring it in comparison to others. I like it in the A5, but it seems a little much in carbine RE’s. Too much preload.
Little known thing about springs is that removing coils increases, not decreases, spring rate. Given identical space to work with, that means the shorter spring (of same material and diameters, etc) has less preload, but higher rate. Something to consider if you are burning brain-calories comparing carbine to rifle to A5 REs.
Its the only non-Colt spring I like, really. I tried to like the lighter Sprincos, but they rust too fast. I wouldn’t swap a working Colt spring for one.
I absolutely agree that the 42 coil in a carbine seems a bit much on preload. But other than the subjective feeling associated with an “authoritative “ shall we say bolt drop, I see no evidence of it being excessive in terms of function. You absolutely don’t want your fingers in there when the bolt drops because it’s going home come hell or high water. It’s notably stiffer when charging, yet you can feel the linearity.
Your experience with the 36 coil spring would be especially noticeable with another 3# of bolt closed preload.
Did you observe any actual problems with the higher preload or was it a subject impression of it being excessive?
I initially got it to try to take better care of my match brass— less damage to brass and ease of recovery of brass was honestly all I expected when I bought it to try.
The dry film coating they ship with gets brittle and flakes off. I grease my spring and buffer lightly with synthetic grease. So far, so good.
I would be interested in others thoughts about effect of Tubb 42 vs 36 used in a:
1) 6.8 SPC rifle, and
2) 6.8 SPC carbine
Thanks in advance for replies.
I've been running the Tubbs 42 coil springs in the A5 RE since they were released. I agree that the range of operation is more broad than a traditional setup. Functionality is greater through out the spectrum of cleanliness, temperature, ammo types, lube, etc.
In 5.56 I'm running an 11.5 suppressed, a 13" with a K can, and a 16" suppressed. My 11.5 is my work gun, and has 15k+ through it's 3rd barrel. So, quite a few rounds with the flat springs. I am a fan of the setup.
I also run a 42 spring in a 14.5" 308 with a K can.
I absolutely agree that the 42 coil in a carbine seems a bit much on preload. But other than the subjective feeling associated with an “authoritative “ shall we say bolt drop, I see no evidence of it being excessive in terms of function. You absolutely don’t want your fingers in there when the bolt drops because it’s going home come hell or high water. It’s notably stiffer when charging, yet you can feel the linearity.
Your experience with the 36 coil spring would be especially noticeable with another 3# of bolt closed preload.
Did you observe any actual problems with the higher preload or was it a subject impression of it being excessive?
I initially got it to try to take better care of my match brass— less damage to brass and ease of recovery of brass was honestly all I expected when I bought it to try.
The dry film coating they ship with gets brittle and flakes off. I grease my spring and buffer lightly with synthetic grease. So far, so good.
In a lightly gassed carbine-RE gun, that was reliably able to eat and eat without cleaning while using a Colt spring, I experienced stoppages while dirty, using .223 ammo. In another carbine-RE gun, this one more heavily gassed, I noted excessive wear on the charging handle and wear near the cam pin relief, that seemed as though it might be accelerated, like on a 416. I don’t think it was at risk of imploding or anything, just something I noticed that made me put a Colt spring back in it and choke the gas down a bit, instead.
Both of the above anecdotes were with the older CS spring, which is stronger than the current SS spring. Both of those guns were my day-to-day beaters, at different times. Unfortunately I don’t have a personally owned carbine-RE gun right now to try the newer spring in.
I don’t think that there’s free lunch, but I do think that the Tubbs spring could possibly be part of the winning formula for a gun that is 50/50 suppressed/loud. I think that the weapon is more forgiving unsuppressed with a spring that is providing more force during locking and unlocking, but practically the same force at the rearmost of travel. I also think that suppressed guns benefit more from that force than the force provided by a stiffer spring, such as the popular Wolff, Sprinco, and Geissele offerings. So, again, I don’t think the lunch is free, but it might both taste better, and be more nutritious, in comparison to other options.
I’ve been working on, as funds allow, putting together an experiment to see if there is really any difference between carbine gas and midlength gas for a 50/50 suppressed/unsuppressed gun, assuming both are gassed lightly in the loud configuration. My hypothesis is the opposite of conventional wisdom. I’ll be using two 14.5” uppers, both with the same model AGB, same model mount, same 762 can, same BCG, same A5 SBR lower. I’ll open the gas block on both until they lock back with the can, then see how many clicks it takes for each to run without it. I was also planning on doing a follow-on where I also switch from H4 to H1 buffers when I pull the can.
After that, I’m doing a third pair of experiments to determine if Tubb’s 36 coil SS makes the guns more or less tolerant of can/no can. If it takes less clicks between min function with and without the can in comparison to the Colt spring, then thats a win.
I also have a SS 42 coil Tubbs, and enough parts to assemble a lower with a carbine RE.
If anyone would like to help me accelerate these experiments coming to fruition, shoot me an IM. I’m like 80% there in parts required to do all of them. The ammo bill is gonna hurt, though.
As for the dry film coating on the SS spring, I have not had any corrosion with mine, despite it chipping/flaking off. I did with the CS model.
I absolutely agree that the 42 coil in a carbine seems a bit much on preload. But other than the subjective feeling associated with an “authoritative “ shall we say bolt drop, I see no evidence of it being excessive in terms of function. You absolutely don’t want your fingers in there when the bolt drops because it’s going home come hell or high water. It’s notably stiffer when charging, yet you can feel the linearity.
.
Sounds similar to when dummies stick an extra heavy recoil spring in their 1911's. Yeah, It can somewhat lessen felt recoil but at the expense of adding a lot more slide dip when that slide does go back into battery.
No thanks. You just made it more difficult to stay on target during a string of rapid fire (same as in the over sprung 1911 example).
Long time 1911 USPSA single stack shooter here.
Stiffer springs increase felt recoil.
You want to run the lightest recoil spring you can reliably run.
I always used 15lb Wilson springs with factory loads and a 14lb with 185gr softball loads.
In an AR, stiffer springs and heavier buffers are the opposite of what you do make one shoot softer.
Look at JP if you want to see how to make one shoot soft.
Long time 1911 USPSA single stack shooter here.
Stiffer springs increase felt recoil.
You want to run the lightest recoil spring you can reliably run.
I always used 15lb Wilson springs with factory loads and a 14lb with 185gr softball loads.
In an AR, stiffer springs and heavier buffers are the opposite of what you do make one shoot softer.
Look at JP if you want to see how to make one shoot soft.
So this is an interesting phenomenon. In motorsports the opposite can often be true. Often times cars and motorcycles are sprung too light, so the suspension bottoms out and gives a harsher ride. Going stiffer in these cases results in a "cushier" ride. I have found something similar in rifles: if the spring is too light, the buffer will smack into the back of the tube and feel harsh, whereas a heavier (but not too heavy) spring eliminates that harshness and slows the recoil impulse.
Obviously there is a balance that must be found here, or you get the bolt moving forward too quickly which also increases the tendency to move the sights off target.
Like I said, lunch isn’t free. The energy used to compress the spring must come from somewhere, and must go somewhere. The Tubbs is not a stiffer spring. It is lighter, with more preload. In Hohn’s case, a eff-ton more preload.
My interest in this spring is not recoil reduction. I’d like to have a rifle function as close to the same as possible, both suppressed and unsuppressed. And I think this could be a part of that puzzle. Or not.
My plan for the experiments I posted earlier won’t work. I just measured a Sentry 7 and its .01” per click. Not precise enough. BRT doesn’t sell gas tubes with holes small enough to make a suppressed 14.5” carbine not run, so that won’t work, either. I might have to try something crazy like a 11.5” mid and a bushel of EZ Tune tubes.
@Clint, do you have any thoughts on this?
Sounds similar to when dummies stick an extra heavy recoil spring in their 1911's. Yeah, It can somewhat lessen felt recoil but at the expense of adding a lot more slide dip when that slide does go back into battery.
No thanks. You just made it more difficult to stay on target during a string of rapid fire (same as in the over sprung 1911 example).
Long time 1911 USPSA single stack shooter here.
Stiffer springs increase felt recoil.
You want to run the lightest recoil spring you can reliably run.
I always used 15lb Wilson springs with factory loads and a 14lb with 185gr softball loads.
In an AR, stiffer springs and heavier buffers are the opposite of what you do make one shoot softer.
Look at JP if you want to see how to make one shoot soft.
With respect, these are not 1911s where the reciprocating mass is above the bore axis. It might be still above a the CoG, but the moment of inertia of a 1911 and an AR aren’t comparable. The reciprocating mass of a 1911 slide is a very high percentage of the gun’s mass relative to an AR.
To be clear, making the gun softer shooting was never the goal. The goal was to be easier on brass. The softer shooting and broader apparent operation envelope were serendipity.
There obviously are ways to make a soft shooting rifle with LMOS, AGB and all those gamer toys. My rifles however are rifles that must work with all the ammo I might feed it. The sporty 3-gun rifles are hyper tuned niche guns with a narrow operating range. They are the opposite of my rifles.
I was a surprised as anyone that a spring I bought to try only for brass preservation during match shooting ends up showing potential as a duty acceptable enhancement.
It might not work for you. It might be awful in a short barrel. It’s a $20 spring. Try it if you want to add to the pool of experience, as opposed to the ocean of conjecture.
A longer spring experiences less change in load with distance than the same spring at a shorter length-- this is because the same twist is distributed across a longer run of wire. So if I have two otherwise identical springs-- one 12" long and the other 24" long, we'd find that compressing them the same distance (say, 3.5" or so) would show the shorter spring to get "stiffer" at a much faster rate. In engineering terms, has has a different spring rate (F=kx, force as a function of spring rate and displacement/distance). They have different rates EVEN THOUGH the wire is exactly the same, the diameter is the same, and all other features are the same.
However, we aren't compressing the springs the same distance. Let's say the compressed spring length inside a carbine RE is 7 inches. (I don't know what the spring length is inside an RE, I'm just pulling 7 inches outa my butt.) That means when the BCG is on battery, the 12 inch spring is compressed 5 inches and the 24 inch spring 17 inches
Takeaway: the 42 coil spring has a lower spring rate (change in load with change in distance) even at higher applied force. This is a good thing. We want the rate as flat as possible.
Why is a flat rate spring a better than a rising rate spring for this application?
The buffer, on the other hand, can only apply inertial force as a function of bolt acceleration. F=MA. No acceleration on the buffer, no force!
This ignores basic physics. Objects at rest tend to stay at rest. Objects in motion tend to stay in motion. It takes more force to start and stop objects with greater mass.
If you want more closed bolt dwell time, a stiffer spring is far more effective than a heavier buffer because the latter can only be relevant AFTER the bolt has started moving.
The buffer & carrier are in motion before the bolt starts unlocking.
Ejection with all lowers was pretty much the same spot at 4:00 with Geco .223 factory and even my weak 8208XBR hand loads, and it didn't seem to matter which lower or buffer weight was in use. Both carbine and A5 lowers ejected to the same spot and locked back on empty mags.
I point that out not that 4:00 ejection is evidence of perfection. Rather, the *consistent* ejection across buffer weights, across carbine vs A5, across factory load vs weak hand load, appears to confirm that the spring makes the gun much less sensitive and less sensitivity means a broader operating envelope.
Ejection angle affected by extractor/ejector setup. Carrier speed has little impact on ejection angle if the extractor and ejector are healthy.
If anyone has experience tuning motorcycle racing suspension, the analogy here is: lower spring rate, but more preload. Kinda like A5 vs carbine...Little known thing about springs is that removing coils increases, not decreases, spring rate. Given identical space to work with, that means the shorter spring (of same material and diameters, etc) has less preload, but higher rate. Something to consider if you are burning brain-calories comparing carbine to rifle to A5 REs.
There is a difference. If you cut a couple of coils off a suspension spring, the preload is the same but the ride height is lowered. Let's say the suspension spring supports 250 lbs of the motorcycle's sprung weight- that is, the spring has a 250 lbs preload. Two coils are cut from that spring. It's still supporting 250 lbs of sprung weight but it lowers ride height- that is, the length of the spring with the same pre-load is shorter.
Cut two coils from an AR recoil spring, "ride height" remains the same (spring length under preload is the same), but preload is reduced.
...The appeal of the 42 coil is that it might be something of a free lunch— less recoil without a reliability penalty or margin reduction.
Springs can change how recoil feels, but they cannot lessen recoil (unless they increase the overall weight of the firearm).
...My plan for the experiments I posted earlier won’t work. I just measured a Sentry 7 and its .01” per click. Not precise enough...
How do you know? How much change in gas flow does each click make in the gas system you plan to test?
A bit more speculation from me as to *why* the 42 coil spring works where it seems it shouldn't.
But before I do, I want to acknowledge that an 18" rifle gas might not prove much of anything. I can't say how it would compare to a 14.5 middy, for example. Lower port pressure for sure, but overall gassing I can't say how representative an 18" rifle gas DD barrel is on the spectrum of over/under gas. I have the impression that DD barrels are a bit on the gassy side for reliability?
Also, I want to point out that this observation was just on two DD barrels- a 16" mid and 18" rifle. It may not represent a nominal barrel or much of anything. So I mean to put a big asterisk by the "runs in anything" comment that I shouldn't have stated in the OP.
All that said, I'm not speculating as to whether they work well in my uppers-- they do, period. My speculation would be *why* they run when on paper they shouldn't, and if this perhaps means we don't understand something as well as we think we do. Or I should say that *I* don't understand it as well as I thought I did.
It did occur to me that the high preload at bolt closed might actually have the effect of raising port pressure a bit by allowing pressure to build a little longer before the bolt unlocks. I've seen testing of the SLR gas block showing notably different muzzle velocity when the block was in "restrict" mode vs "bleed off" with the bleed off dropping MV. I'm wondering if having the bolt held closed longer (bit more preload) might mimic the effect observed on the AGB testing where not bleeding off the gas as quickly showed slightly higher pressures in the port and behind the bullet.
We have to keep in mind that pressure in the gas tube and gas key rises on a curve, albeit an incredibly fast one. At some point on that curve, enough pressure has built to begin pressurizing the chamber of the BCG and push the bolt forward and BCG rearward. But this is NOT the peak pressure. The pressure will continue to rise until either the gas key is disengaged from the tube OR the bullet leaves the barrel.
So *if* the high preload of the 42 coil spring is holding the bolt closed momentarily longer until a point higher on the pressure curve is reached, this would cause the rifle to act as if it had more gas and *might* explain why the high preload seems to work even without an obvious over-gas situation.
If this theory is valid, I hypothesize that one might expect to see a difference in muzzle velocity between a high preload 42 coil spring and a standard carbine or rifle spring. I have not tested this. It would require probably 30 rounds of chrono data each for the 42 coil spring vs a regular spring. Even then it might not pass a t-test for significance.
Anyway, I appreciate your indulgence in my thinking out loud here. I'm not trying to sell anyone on anything or suggest this is the be all for every AR, and I apologize if my post suggested that. I reread it and can see how it might come across that way and I figured I'd rather post this mea culpa than edit the OP.
I get hung up on things that I don't understand (i.e. why this spring seems to work where it shouldn't) so group-processing it with other curious people is helpful to me.
Thank you.
If you’re wanting to build a dead-nuts reliable duty gun, you build the gun around the ammo.
Trying to build a weird 1-off gun around ammo that you may or may not even have is starting from the wrong angle IMO.
Long time 1911 USPSA single stack shooter here.
Stiffer springs increase felt recoil.
You want to run the lightest recoil spring you can reliably run.
I always used 15lb Wilson springs with factory loads and a 14lb with 185gr softball loads.
In an AR, stiffer springs and heavier buffers are the opposite of what you do make one shoot softer.
Look at JP if you want to see how to make one shoot soft.
We will have to agree to disagree about how more spring increases perceived / felt recoil...
Either way though, that recoil is still there if the load remains the same. You can definitely change how the gun tracks as it cycles with springs / FPS's, etc. but you are not getting rid of the recoil without changing the load.
On my comped 1911's - Full power loadings are not going to cycle the slide at all with a 15lb recoil spring. That empty brass is staying in the chamber and you can forget about the thing called 'semi-auto'. LOL! :) With a normally radiused FPS and a standard weight hammer springs I need to drop to about 12lbs on the recoil spring to 'reliably' be able to cycle and lock back on an empty mag. If I up the hammer spring weight or go with a flat bottom FPS that recoil spring weight will need to be reduced even more to be 'reliable' and cycle properly.
Imagine full power loadings with a powder (like AA#7) that actually produces enough gasses to be able to 'work' a comp (and reduce muzzle climb) while at the same time being around 10 to 12lbs on your recoil spring weight affecting your slide dip when things go back into battery... That makes for one hell of a flat tracking 1911 my friend! :)
Find even one A Class or better shooter who says that stiffer springs track flatter than lighter...
With respect, these are not 1911s where the reciprocating mass is above the bore axis. It might be still above a the CoG, but the moment of inertia of a 1911 and an AR aren’t comparable. The reciprocating mass of a 1911 slide is a very high percentage of the gun’s mass relative to an AR.
To be clear, making the gun softer shooting was never the goal. The goal was to be easier on brass. The softer shooting and broader apparent operation envelope were serendipity.
A simple experiment you can do at home with no ammo expended at all:
With your bolt locked back on an empty mag and nothing in the chamber look through your sights and hold as steady as you can while you hit the bolt release. Observe what happens to your sight picture as that bolt slams home...
Repeat experiment with a regular weight spring and chime back in with your findings. :)
Same sort of experiment can be done at the range using paper targets and live ammo. Send two or three rounds downrange as fast as you can with the heavy as hell spring and then swap paper and try same test with the standard weight buffer spring.
I completely understand where you are going with your thoughts about going easy on the brass. 100% with you on that being a good idea and if you can tune your gun to plant that brass exactly where you want to (without sacrificing too much elsewhere) then power to you.
However, we aren't compressing the springs the same distance. Let's say the compressed spring length inside a carbine RE is 7 inches. (I don't know what the spring length is inside an RE, I'm just pulling 7 inches outa my butt.) That means when the BCG is on battery, the 12 inch spring is compressed 5 inches and the 24 inch spring 17 inches.
You are only off by 1/4 inch. Your butt is pretty good at estimation.
Why is a flat rate spring a better than a rising rate spring for this application?
It isn't, necessarily. Flatter spring rates are desired for main/recoil springs to keep the force required to hold the bolt open (maximum compression) with reasonable limits while the force holding the bolt closed (minimum compression) enough to reliably strip and feed a round. These should not be more that 6 to 12 pounds. If you keep the force produced by spring to 7.5 pounds through the whole compression, you actually may while up with a bolt carrier bottoming out with higher velocity, as the energy absorbed by the spring is the area under the curve.
https://i.imgur.com/FQwos8n.png
This ignores basic physics. Objects at rest tend to stay at rest. Objects in motion tend to stay in motion. It takes more force to start and stop objects with greater mass.
No free lunches in physics.
If you want more closed bolt dwell time, a stiffer spring is far more effective than a heavier buffer because the latter can only be relevant AFTER the bolt has started moving. The buffer & carrier are in motion before the bolt starts unlocking.
NO. You are not going to put a spring in an AR strong enough to alter "dwell time". The force from the pressure on the piston pushing it open is in the neighborhood of 400 pounds. the mass of the bolt, carrier, and buffer is about a pound, calculate the initial acceleration of the reciprocating mass if the spring load is 6 pounds or 12 pounds . . . it's about 1.5% difference, that is not going to make an appreciable difference in time to move the mass 0.325 inch . . .
In fact, this statement is flat wrong: "a stiffer spring is far more effective than a heavier buffer". Changing the mass makes a greater impact on opening time than spring rate or preload. As we have seen, doubling the spring rate (100% increase) reduces the initial acceleration by only 1.5%, but a 10% increase in total mass (going from a standard buffer to an H2), decreases the initial acceleration by 10%.
Physics shows that inertia is much better at stopping things than springs, at least spring that people can manipulate.
Ejection angle affected by extractor/ejector setup. Carrier speed has little impact on ejection angle if the extractor and ejector are healthy.
As long as it is not throwing spent cases down your shirt, does ejection angle even matter?
If anyone has experience tuning motorcycle racing suspension, the analogy here is: lower spring rate, but more preload. Kinda like A5 vs carbine...Little known thing about springs is that removing coils increases, not decreases, spring rate. Given identical space to work with, that means the shorter spring (of same material and diameters, etc) has less preload, but higher rate. Something to consider if you are burning brain-calories comparing carbine to rifle to A5 REs.There is a difference. If you cut a couple of coils off a suspension spring, the preload is the same but the ride height is lowered. Let's say the suspension spring supports 250 lbs of the motorcycle's sprung weight- that is, the spring has a 250 lbs preload. Two coils are cut from that spring. It's still supporting 250 lbs of sprung weight but it lowers ride height- that is, the length of the spring with the same pre-load is shorter.
Cut two coils from an AR recoil spring, "ride height" remains the same (spring length under preload is the same), but preload is reduced.
Actually the analogy is totally wrong, the two systems compared are completely different.
If you cut a coil or two off a vehicle suspension, you have shortened the working room for the spring, assuming you haven't moved the travel limiters, and changed the spring rate.
Springs can change how recoil feels, but they cannot lessen recoil (unless they increase the overall weight of the firearm).
Something a lot of people don't seem to understand.
How do you know? How much change in gas flow does each click make in the gas system you plan to test?
And, how much gas flow is required to make a noticeable difference?
There is another issue with the very long 42 coil spring.
A very long spring with a few coils has a very high helix angle. Compare the angle off the axis of wire on the two springs
https://i.imgur.com/DtkXKx1.jpg?2
As the spring compresses the wire twists, the more the wire twists, the higher the stresses are in the wire (see below)
https://i.imgur.com/nz6gqL8.png
Optimally spring should be kept to a working length of not less than 50% of the free length. The standard AR spring has a free length of 10.70 inches long and the compressed length (bolt closed) of about 6.75 inches, and 3 inches fully compressed (so, a range of 41% to 71%), if the 42 coil spring is 24 inches long then the working range is 71% to 88%. Even for a flat spring, I would consider this a bit high.
What you really want is a long spring with a lot of coils, this gives a low helix angle, so low stress, a fairly flat spring rate in the middle range, but the down side if the solid length is long.
I'll stick with my A5 buffer and springs, thanks very much.
If I double the spring force holding the bolt closed, then the initial acceleration of the bolt to the rearward would be cut in half.
NO.
The acceleration of the bolt group is the total force of the bolt, divided by the total mass.
The total force on the bolt is the piston pressure minus spring force:
A = (Fp - Fs)/m
So:
A2 = (Fp - 2Fs)/m
A1 = (Fp - Fs)/m
Where:
A2 is the new acceleration
A1 is the acceleration with a standard spring
m is the bolt/carrier/buffer mass (constant)
Fs is the standard spring force
We can see the m will cancel out, yielding:
A2 = (Fp - 2Fs)
A1 ... (Fp - Fs)
Let's put some numbers in the equation:
The piston force (Fp) is around 400 pounds, and the standard spring pre-load (Fs) is 6 lbs, so doubling the spring load gives 2Fs as 12 lbs:
A2 = (400 - 12)
A1 ... (400 - 6)
or,
A2 = (388)
A1 ... (394)
a little math and A2/A1 = .98478, or 1.5% drop in velocity.
If the bolt has half the acceleration rearward, then the "apparent weight" of the buffer is less. Let's say for illustrative purposes that in one case, the bolt accelerates rearward at 20g and in the other, it heads rearward at 10g (where "g" is acceleration of gravity at ~ 32.2 ft /sec^2).
NO, just no.
The mass of the buffer is unchanged, therefore its inertial response to acceleration is the same. The buffer is not forcing the movement but resisting it.
The acceleration is different because the force is different (by a whopping 1.5%)
So I understand that a spring change from a standard spring to one of these extra long flat springs won't change the amount of recoil, so my question is, will it change the feel of the recoil to something better?
So I understand that a spring change from a standard spring to one of these extra long flat springs won't change the amount of recoil, so my question is, will it change the feel of the recoil to something better?
Depends on what you think better is.
Personally I absolutely can’t stand the way a heavy buffer setup cycles. Seems like the dot dances forever and I have to work a lot harder to keep it on target. It feels smoother, but targets and timers DO NOT lie.
Depends on what you think better is.
Personally I absolutely can’t stand the way a heavy buffer setup cycles. Seems like the dot dances forever and I have to work a lot harder to keep it on target. It feels smoother, but targets and timers DO NOT lie.
I'm with you. I shoot 3gun and some USPSA and for my pistols I run lighter springs trying to flatten out the recoil impulse. Looking for the straight back and straight forward effect. On AR's I run them fairly stock. H1 buffer in my carbine and midlength. Standard rifle buffer in my 3gun rifle. Nothing fancy. Just wondering if these flat springs would benefit me in anyway.
What you really want is a long spring with a lot of coils, this gives a low helix angle, so low stress, a fairly flat spring rate in the middle range, but the down side if the solid length is long.
Academically would conical springs be useful? If the coils nest the solid length of each one is only the thickness of the wire. A stack of these would fit more coils in the same length I think, but it would consume the internal space used for the buffer. If that could be addressed somehow, perhaps tungsten weights inside the carrier, would it be a more ideal spring system?
Lysander, I was hoping you would chime in. Thank you for contributing, I always enjoy your technically detailed posts.
How do you know? How much change in gas flow does each click make in the gas system you plan to test?
https://www.m4carbine.net/showthread.php?227778-Adj-gas-block-adventures-(1168)
Take a look at the numbers in that thread, and you’ll see what I mean.
Academically would conical springs be useful? If the coils nest the solid length of each one is only the thickness of the wire. A stack of these would fit more coils in the same length I think, but it would consume the internal space used for the buffer. If that could be addressed somehow, perhaps tungsten weights inside the carrier, would it be a more ideal spring system?
Conical springs that will nest have there place, but let's think about it, in order to nest, each coil diameter must be at least two wire diameters less that the one in front of it. If you have a 1 inch diameter spring with 0.0625 diameter wire, you get 8 coils before you run out of room, so realistically 5 or 6 coils maximum. You would lose the 3 inches of buffer that normally resides inside the coils. The spring rate is highly non-linear (which is the real reason to choose a conical spring), which complicates things. So in this case it creates more problems than it fixes.
Theoretically, if you want a "fast gun", one that stays on target for a follow-up shot, you need to do a few things:
1) Reduce the gas so it just barely locks back reliably, this means the lowest possible rearward bolt velocity, and
2) Reduce the spring tension, when closed to the minimum that will reliably feed, chamber, and lock, this means the lowest possible forward bolt velocity.
It is impossible in a AR to not have the buffer bottom out on the back of the extension due to the need for a reliable extraction and ejection bolt velocity, and the limited working length of the spring in the extension. The lowest possible bolt velocity means the softest impact of the buffer against the extension, thus your shoulder. Low velocity also means low rebound, so the initial forward speed is lowest. The lowest spring tension closed means the lowest forward velocity of the bolt as it returns home. The bolt going home is usually what pushes the sights off, it doesn't matter if it pushes down, up, or sideways, one pound of steel and aluminum slamming into 5 or 6 pounds of rifle is going to make it move somewhere; more than the 1/16 inch width of the front sight (or red dot.)
And last, reduce the weight of the reciprocating mass (carrier and buffer) as much as possible, the less mass you have bouncing off the inside of the rifle, the less it will jump around.
Obviously, this is all a balancing act as if the mass is too light, you don't have enough momentum to fed and chamber, unless you increase the velocity to get more energy, which means more gas or more spring. And if the spring is too light, increased friction from dirt and fouling will start to suck off energy.
Have fun playing with springs, buffers and adjustable gas blocks...
Conical springs that will nest have there place, but let's think about it, in order to nest, each coil diameter must be at least two wire diameters less that the one in front of it. If you have a 1 inch diameter spring with 0.0625 diameter wire, you get 8 coils before you run out of room, so realistically 5 or 6 coils maximum. You would lose the 3 inches of buffer that normally resides inside the coils. The spring rate is highly non-linear (which is the real reason to choose a conical spring), which complicates things. So in this case it creates more problems than it fixes.
Thank you.
https://www.m4carbine.net/showthread.php?227778-Adj-gas-block-adventures-(1168)
Take a look at the numbers in that thread, and you’ll see what I mean.
I saw that. It doesn't measure flow, nor does it measure how much change in flow each click makes. Is one click equal to a change in port diameter of .001"? .005"? .0005"?
Can gas flow be controlled fine enough that an AR will consistently lock back on a carbine buffer, but not an H buffer? Is having flow control that fine practical? (The higher the gas port pressure, the greater the difference in flow each .0005" change makes.)
I'm inclined to believe carbine,H, H2, A5H2 and rifle buffers will all lock back using the same minimal gas flow, but the lighter buffers bottom out harder, giving sharper recoil.
I can't make heads or tails of your results. For example, I don't know what "30DSk" means
PS- Gas operated firearms run off residual pressure. That's pressure in the bore after the bullet exits the muzzle. That means the AR BCG group doesn't reach operating pressure until the bullet has left the barrel.
I saw that. It doesn't measure flow, nor does it measure how much change in flow each click makes. Is one click equal to a change in port diameter of .001"? .005"? .0005"?
The adjustment screw has a a cylindrical portion that uncovers 0.01” of port per click. This is obviously not particularly precise, and you’ll note that in my tests, there’s not a big difference in number of clicks used in any unsuppressed configuration, or between any of the suppressed configurations.
Can gas flow be controlled fine enough that an AR will consistently lock back on a carbine buffer, but not an H buffer? Is having flow control that fine practical? (The higher the gas port pressure, the greater the difference in flow each .0005" change makes.)
I'm inclined to believe carbine,H, H2, A5H2 and rifle buffers will all lock back using the same minimal gas flow, but the lighter buffers bottom out harder, giving sharper recoil.
.
Probably not. Its not quite precise enough to arrive at different settings for a 762 vs 556 can, though the 762 can feels a little light, and the 556 can is gassy. It might be practical for finer adjustments to be available; I don’t really know. It does not look easy to design such a device.
I’m also inclined to believe that different weight buffers will lock back on the same setting, simply because the settings are so coarse. And because buffers don’t make as big a difference in bolt velocity as we’d like them to.
I can't make heads or tails of your results. For example, I don't know what "30DSk" means
Its a silencer.
Sorry I couldn't get back to this thread until now.
However, we aren't compressing the springs the same distance. Let's say the compressed spring length inside a carbine RE is 7 inches. (I don't know what the spring length is inside an RE, I'm just pulling 7 inches outa my butt.) That means when the BCG is on battery, the 12 inch spring is compressed 5 inches and the 24 inch spring 17 inches
I'm not explaining it very clearly then. The bolt travel is the same regardless of what spring you use. Yes, a spring with longer free length is compressed more to be installed. But let's not confused spring *rate* with spring *force*. The long Tubb spring has lower rate at a higher force, just as 1168 observed with his apt comparison to suspension preload. The higher force of the longer spring is due to it being compressed further even at a lower rate (i.e. moving farther along its curve vs moving the curve itself).
Why is a flat rate spring a better than a rising rate spring for this application?
In a word, timing. From a basic energy storage perspective, linearity doesn't matter. All that matters is the area under the curve. If the dwell time at the rear didn't matter, linearity wouldn't matter. But if I have a super progressive spring where it's 3# bolt closed at 25# bolt open, the bolt flies past the magazine and comes back past the magazine before the mag spring can fully present the next round. So for timing and also the general benefit associate with retarding bolt unlock, we want to do as much of the force application up front as practicable. (for you suspension guys, this is the idea behind Digressive Shock Valving like Bilstein uses.)
This ignores basic physics. Objects at rest tend to stay at rest. Objects in motion tend to stay in motion. It takes more force to start and stop objects with greater mass. Only at the same acceleration rate is this true. But if there is no acceleration, then the equation says the force MUST be zero. This doesn't ignore basic physics, it's the application of Newtonian mechanics. Until and unless the buffer mass is trying to being accelerated (i.e. moving) it has no inertial resistance, apart from the instantaneous first impulse of acceleration which technically occurs at an infinite rate. (all accelerations from zero occur instantaneously at an infinite rate).
The buffer & carrier are in motion before the bolt starts unlocking. True, and thank you for that reminder. It clear I was partially misapplying the point above about buffer inertia.
Ejection angle affected by extractor/ejector setup. Carrier speed has little impact on ejection angle if the extractor and ejector are healthy. Agree, which is why only the change (or lack of it) in angle was notable. Also, this is a brand new Toolcraft carrier so its springs couldn't be fresher. The testing I did was the first rounds the carrier ever saw.
There is a difference. If you cut a couple of coils off a suspension spring, the preload is the same but the ride height is lowered. Let's say the suspension spring supports 250 lbs of the motorcycle's sprung weight- that is, the spring has a 250 lbs preload. Two coils are cut from that spring. It's still supporting 250 lbs of sprung weight but it lowers ride height- that is, the length of the spring with the same pre-load is shorter.
Cut two coils from an AR recoil spring, "ride height" remains the same (spring length under preload is the same), but preload is reduced. Technically preload is the same only because it's determined by the mass that is compressing the spring (sprung mass of the car). But you have changed the spring rate of the spring and the same mass will cause it to achieve equilibrium at a different point. Essentially, you have two different spring curves and the same force on each curve will be a different amount of compression as a result if you were to graph F=kx for each.
Springs can change how recoil feels, but they cannot lessen recoil (unless they increase the overall weight of the firearm). Also agreed, of course. A basic free body diagram shows this convincingly enough. Springs, however, can affect the perception of recoil by manipulating the time over which that recoil is experienced, and in the case of ARs in particular, by preventing the massive DUMP of energy into the buttstock that is associated with a massively under sprung/overgassed gun. A gun that expends most of the recoil energy smoothly compressing a spring and has no spike in the force curve (i.e. buffer bottoming out at high speed) will be perceived as less recoil because it is "smoother." That is precisely my observation using this spring. Obviously not less recoil, but it is a different curve for the same area, and a curve that is more pleasant to shoot and more easily managed (IMO) in terms of sight recovery. If you could place an instrumented load cell or accelerometer at the buttstock and collect high speed data, it would be apparent graphically when the data is processed.
Revisiting the suspension analogy-- suspension cannot reduce the energy input to the car by going over a bump at a given speed. But it absolutely affects how the occupants of the car will experience that bump, as can be decisive as to how the control of the car is maintained by preserving wheel contact with the road.
A simple experiment you can do at home with no ammo expended at all:
With your bolt locked back on an empty mag and nothing in the chamber look through your sights and hold as steady as you can while you hit the bolt release. Observe what happens to your sight picture as that bolt slams home...
Repeat experiment with a regular weight spring and chime back in with your findings. :)
Same sort of experiment can be done at the range using paper targets and live ammo. Send two or three rounds downrange as fast as you can with the heavy as hell spring and then swap paper and try same test with the standard weight buffer spring.
I completely understand where you are going with your thoughts about going easy on the brass. 100% with you on that being a good idea and if you can tune your gun to plant that brass exactly where you want to (without sacrificing too much elsewhere) then power to you.
Testing reaction without the initial action is pointless. You want me to admit that a stiffer spring returns the bolt more aggressively? Well yes, it does. But there's two sides to this and looking at only one of them is at the minimum incomplete. What matters is how the SUM of the actions performs, no? Compression and return, right?
There is another issue with the very long 42 coil spring.
A very long spring with a few coils has a very high helix angle. Compare the angle off the axis of wire on the two springs
https://i.imgur.com/DtkXKx1.jpg?2
As the spring compresses the wire twists, the more the wire twists, the higher the stresses are in the wire (see below)
https://i.imgur.com/nz6gqL8.png
Optimally spring should be kept to a working length of not less than 50% of the free length. The standard AR spring has a free length of 10.70 inches long and the compressed length (bolt closed) of about 6.75 inches, and 3 inches fully compressed (so, a range of 41% to 71%), if the 42 coil spring is 24 inches long then the working range is 71% to 88%. Even for a flat spring, I would consider this a bit high.
What you really want is a long spring with a lot of coils, this gives a low helix angle, so low stress, a fairly flat spring rate in the middle range, but the down side if the solid length is long.
Indeed the downside of few coils relative to length is helix angle. But helix angle doesn't directly translate into either yield point or fatigue unless you are comparing otherwise identical springs. And what we really care about is fatigue. Well, maybe a little about yield to the degree it affects fatigue--fatigue life plummets drastically the closer we operate to the yield stress. If it didn't affect fatigue, we wouldn't really care about yield after the initial install if the rest of the properties met our needs.
My understanding is that round wire spring design rules don't directly translate to flat wire springs because of how the stress is distributed within the wire (I haven't seen any FEA on this, but I have on our ovate wire springs). And the rules of thumb you mention are ones I've heard before but obviously vary a great deal with actual material and temper and such, not to mention spring wire geometry (flat, braid, oval, etc). We use oval wire for our engine valve springs because it has superior fatigue properties relative to round wire and better harmonics also.
For this 42 coil spring, the compression percentages are high because of the 19.5" free length, but whether or not that is excessive for this spring remains to be seen. I'll run it and see how it does. Obviously too early to tell anything after only 1k rounds...
I suspect that the flat wire's very compact solid height (shorter than the mil spec roundwire spring) and the fact that it still hasn't yielded when it is compressed solid might be reason to expect it will perform OK.
Because in the end, what really matters is the stress distribution and how close that is to the yield strength of the material when it cycles because that's what drives fatigue. All the rules about length and helix angle and such are useful rules thumb, but aren't a substitute for actually knowing the stress and fatigue properties of whatever is cycling.
I'll be the first to say that I don't know what the fatigue and yield stress properties are of this spring. But I do find it interesting that my pistol slides with flat wire recoil springs are similarly close to solid height as this spring is when fully compressed, so maybe it's not so bad?
There's also the pandora's box of spring dynamics and the modal resonance of the spring. I've seen comments to the effect that it's the poor damping and low modal frequency of the mil spec spring are the big contributors to its fatigue. This is consistent with my professional experience as well in other springs. The peak stress that occurs during an amplitude peak under resonance can be many times higher than a static stress.
I have no test data on the dynamic properties of these Tubb springs but I can tell you that you experience a lot less SPROING when shooting them, and I consider this to suggest a lot less modal resonance in the spring and almost certainly a lower peak amplitude during that resonance. If true, this would suggest that it might be able to handle a lot more static stress because the dynamic stresses are so much less.
I think you'd agree that it is cyclic stress that kills springs more than static stress. I think it's possible--maybe even likely- that the higher mean stress of stuffing this 42 coil spring into a carbine tube (or even an A5 at only 3/4" longer) is fully offset by better dynamic properties.
NO.
The acceleration of the bolt group is the total force of the bolt, divided by the total mass.
The total force on the bolt is the piston pressure minus spring force:
A = (Fp - Fs)/m
So:
A2 = (Fp - 2Fs)/m
A1 = (Fp - Fs)/m
Where:
A2 is the new acceleration
A1 is the acceleration with a standard spring
m is the bolt/carrier/buffer mass (constant)
Fs is the standard spring force
We can see the m will cancel out, yielding:
A2 = (Fp - 2Fs)
A1 ... (Fp - Fs)
Let's put some numbers in the equation:
The piston force (Fp) is around 400 pounds, and the standard spring pre-load (Fs) is 6 lbs, so doubling the spring load gives 2Fs as 12 lbs:
A2 = (400 - 12)
A1 ... (400 - 6)
or,
A2 = (388)
A1 ... (394)
a little math and A2/A1 = .98478, or 1.5% drop in velocity.
NO, just no.
The mass of the buffer is unchanged, therefore its inertial response to acceleration is the same. The buffer is not forcing the movement but resisting it.
The acceleration is different because the force is different (by a whopping 1.5%)
Thank you for the correction. I know it takes time to post something like that, and I'm in your debt.
Do you think it's fair to say they that the effect of higher preload on bolt timing is largely inconsequential? Because even if we tripled bolt closed force, it's still a trifle compared to the piston power acting inside the BCG? (What is the technical name for that expansion chamber?)
Thank you for the correction. I know it takes time to post something like that, and I'm in your debt.
Do you think it's fair to say they that the effect of higher preload on bolt timing is largely inconsequential? Because even if we tripled bolt closed force, it's still a trifle compared to the piston power acting inside the BCG? (What is the technical name for that expansion chamber?)
The time from ignition to unlocking is largely independent of the spring due to the large difference in forces. This time is mainly governed by the mass, gas port size, length of gas tube, and how leaky the system is.
As to the spring, there is no sharp demarcation between the elastic region and the plastic region on the stress-strain diagram, they bleed into one another. Continued strain at the upper end of the "elastic range" will result in plastic behavior over time. That is the reason for the rule-of-thumb to keep the working length of a spring at 50% of the free length. Continued compression of the spring beyond about 50% leads to accelerated compression set and reduced spring life due to shortening and loss of spring rate. And this can happen while keeping the stress below the fatigue limit. In general, firearm recoil and magazine springs are over-compressed (working beyond 50% length) to begin with. This is due to the limited space available, and the required movement distances, and why these spring in guns need replacing at regular intervals, measured in thousands of cycles, where as isolation springs under machinery can last for several decades with lives measured in millions of cycles.
I am just very leery of stuffing more spring in a space that didn't have enough room to begin with.
I'm aware of the fuzzy area between elastic and plastic region which is why the offset (often 0.2%) convention was adopted. And you are of course correct that fatigue can set in before one would consider a stress to be "yield" at the macro level.
I've decided that I'm going to run the carbine lower as long as I can with this spring and just see how long it lasts. If the 42 coil holds up in the carbine tube, it will obviously fare better in the A5 and better still in a Rifle extension. A friend is running the same spring in two separate lowers (one rifle, the other carbine) and likewise having very good luck with it thus far.
Fatigue and potential durability concerns aside, the spring does seem to increase the performance envelope and make the gun really smooth. Time will tell if it's a pyrrhic victory or not.
Fatigue and potential durability concerns aside, the spring does seem to increase the performance envelope and make the gun really smooth. Time will tell if it's a pyrrhic victory or not.
LOL!
No matter how many guys try to explain to you how what you did was not an 'upgrade' you continue to believe it was.
:)
LOL!
No matter how many guys try to explain to you how what you did was not an 'upgrade' you continue to believe it was.
:)
Ok,.....your opinion unless you have data to prove otherwise.
Convince me otherwise.
I'm going to try a 36 coil. See if I can discern any difference.
LOL!
No matter how many guys try to explain to you how what you did was not an 'upgrade' you continue to believe it was.
:)
Just so I’m sure I understand, is it your contention that I should fully discount my firsthand experience with a rifle I built in favor of the assessment of internet strangers who have never fired the gun? And I should also discount the successful use in an otherwise factory DDM4? And the successful use by several others in my immediate acquaintance whose rifles I have seen and often shot?
I’m sorry I might have misled you into thinking I was soliciting input on whether this was a good idea or not. Not at all. Rather I was observing that it works, works very well, and inviting discussion on the reasoning why it might work so well.
Do you have meaningful round count experience with this spring in a similar rifle in carbine or A5 extensions? I apologize if I missed your sharing the result of such. The only open question is durability and if your experience sheds light on that, please share it.
I'm going to try a 36 coil. See if I can discern any difference.
I’m looking forward to your assessment.
I’d be surprised if you found anything more than a subtle difference with the shorter 36 coil version. My internet “research” mostly showed people liking the reduced “sproing” for similar function and reliability with possibly a bit smoother impulse.
I tried the 42 coil because it can be shortened to 36, whereas a 36 cannot be extended to 42. I ended up never shortening any of mine so I have no experience with 36 coil versions and can only convey the internet hearsay of others.
I shot my 3gun rifle at the range Thursday. I shot 5 with the flat wound and then 5 with stock round coil spring. I did that a couple of times. Got to watch that ammo. The load was my own, Hornaday 62 gr FMJ-BT over 24 grs. of H335. I did shoot some more, maybe, 30-40 rounds with the flat wound. No malfunction. My impression, and that's all it is, is that the flat wound spring is ever so slightly smoother in operation. It is very subtle, but I could tell the difference. I liked it, and am looking to improve my rifles in even small relatively inexpensive ways. I'll buy a couple more. It also mitigated that sproing sound quite a bit, if it matters.
I've used the 42 coil for about 12-13 years starting with a carbine RE then to a A1 rifle stock, RE and finally the A5 RE, and H2 buffer for the last 9-10 years. have never had any issues with any of the combos with multiple uppers from a overgassed 16" upper to 1 dedicated suppressed 11.5 upper with a microtune GB with a .049 port insert and finally a P/W 14.5 BCM EWL and BCM GB. most of my ammo has been hand loads for the last 10 years, but I inherited a small cache of lake city 85 55 gr that was very juicy gas wise but my present configuration ran with out a hiccup at a recent match with little difficulty getting the obligatory double tap on several runs. this is also my original spring for the last 13 years just did a bcg check to see if it was bottoming out, still have the proper 2 quarters gap. I have parts accumulating for a service rifle optic rig so definitely get a fresh one to try the 36 coil trick
I am not an engineer, but I am an inveterate tinkerer.
All things being the same, my experience with (16-inch carbines and 20-inch) USAMU "National Match" M16s and AR-10s, heavy (XH and H3) buffers and Tubb springs give me less perceived recoil, less movement off-target (faster recovery for rapid-fire strings), and abuses my brass a whole lot less with moderate and top-end pressure precision loads.
I am not an engineer, but I am an inveterate tinkerer.
All things being the same, my experience with (16-inch carbines and 20-inch) USAMU "National Match" M16s and AR-10s, heavy (XH and H3) buffers and Tubb springs give me less perceived recoil, less movement off-target (faster recovery for rapid-fire strings), and abuses my brass a whole lot less with moderate and top-end pressure precision loads.
Which Tubb springs are you using, the 36 or 42 coil?
In A5 tubes for the 5.56, the 5.56 spring.
In A5 tubes for the 7.62, the AR-10/SR-25 spring.
In A5 tubes for the 5.56, the 5.56 spring.
In A5 tubes for the 7.62, the AR-10/SR-25 spring.
Try the 42 coil in A5 5.56 guns. I’m curious how it runs for you.
Straight Shooter
01-24-21, 20:56
Try the 42 coil in A5 5.56 guns. I’m curious how it runs for you.
Got one ordered, per the info in your thread, sir. Eager to see myself! Thanks for that info.
Try the 42 coil in A5 5.56 guns. I’m curious how it runs for you.
The 42 coil runs excellent for me, supp/unsupp with a properly ported barrel.
The 42 coil runs excellent for me, supp/unsupp with a properly ported barrel.
Likewise, hence this thread to compare to others. Thanks for adding your experience.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.