View Full Version : DD 16” midlength gassing
Are 16” DD rifles known to be overgassed? I know their 10.3” barrels were at one time, but I haven’t really heard anything on the 16” barrels. This is to spin off my threat about ammo temperature variations since I wonder if it’s gun problem instead. According to DD their 16” midlengths have a 0.073” gas port, and I got a complete factory V9 rifle so it’s standard carbine extension and H buffer. With Wolf Gold WM193 it’s ejecting 2 o’clock, sometimes even more forward, and it was doing this when I shot this weekend when it was warm but not that hot, mid 80s overcast. I tried several 5.56 loads and it was consistently doing the same thing. Round count is ~1400.
On paper this rifle should feel soft to shoot, but compared to my friend’s build, which is BA upper, Aero M16 BCG, Spikes lower, mine feels more gassy. His gas port is 0.078” and with carbine buffer. His ejection is right around 3 o’clock. Shooting his rifle with WM193 feels like shooting mine with PMC Bronze, and he hasn’t had any problems, though I personally haven’t seen his rifle being shot in cold weather.
MikhailBarracuda91
08-02-21, 07:41
I wouldn't worry about it. Daniel Defense is a quality product. My BCM middy pin gauged at .076 and it actually feels gassier than my brother's LMT carbine.
I would just roll with what you got, those guns shoot lights out. And a little bit of extra gas only insures proper function
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If it really bothers you, you can go with one of BRT's gas tubes, and/or an H2 buffer. I went with one of their gas block inserts, when they still sold those, on a BCM pencil barrel as I felt the recoil impulse was way more than it should have been and it really helped.
Another option is a quality adjustable gas block, an example is SLR, and you can tune it for lockback w Wolf Gold or PMC. Gas port size becomes irrelevant, and if adjustment screw freezes w carbon, so what, unless a suppressor is being used. Even then, a charging handle w a raised lip to block gas will help.
Mark
I thought they were .074” which is fine. One of the best gassed 16” mids you can get.
pointblank4445
08-02-21, 15:07
I thought they were .074” which is fine. One of the best gassed 16” mids you can get.
My last 3 have gauged out at 0.076"
I thought they were .074” which is fine. One of the best gassed 16” mids you can get.
When I asked, they said that their 16” midlengths had 0.073” gas ports
My last 3 have gauged out at 0.076"
I thought that’s the gas port size of their 14” midlengths.
Put in H2 buffer.
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El Vaquero
08-08-21, 02:36
I have a DD 14.5” mid length and it’s a very soft shooter.
Put in H2 buffer.
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Or, be confident that when you buy a top shelf rifle, the engineers know something, and just shoot it.
MikhailBarracuda91
08-08-21, 07:42
Or, be confident that when you buy a top shelf rifle, the engineers know something, and just shoot it.Agreed [emoji106]
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Or, be confident that when you buy a top shelf rifle, the engineers know something, and just shoot it.
^^^ This ^^^
pointblank4445
08-08-21, 09:58
I thought that’s the gas port size of their 14” midlengths.
I have one and it also gauged at 0.076"...
Or, be confident that when you buy a top shelf rifle, the engineers know something, and just shoot it.
Or, pop the gas block off and discover that damn near every ‘top shelf’ manufacturer ports barrels for the dirt clod Tula crowd.
Leonidas24
08-08-21, 11:05
Or, be confident that when you buy a top shelf rifle, the engineers know something, and just shoot it.
Or, pop the gas block off and discover that damn near every ‘top shelf’ manufacturer ports barrels for the dirt clod Tula crowd.
I'm with 17K. Colt did it right on the 6960 at .071.
Or, pop the gas block off and discover that damn near every ‘top shelf’ manufacturer ports barrels for the dirt clod Tula crowd.
Maybe. But it sure seems like every topic about “hey guys, I have a gun that eats ammo” devolves into ****ing with buffers pretty fast.
There's probably not a discernible difference between a .071 and a .073 gas port.
Keep in mind that felt recoil is a sum of parts and not just a gas port size. So, barrel length and profile, gas port, BCG efficiency, gas tube interface, buffer system, and overall weight of the rifle.
Maybe. But it sure seems like every topic about “hey guys, I have a gun that eats ammo” devolves into ****ing with buffers pretty fast.
This is M4C.
A good portion of the crowd demands that their gun run with PMC Bronze, A5H4, Sprinco Green or Geissele Super42.
And then complain about the barrel being overgassed.
Well no shit.
This is M4C.
A good portion of the crowd demands that their gun run with PMC Bronze, A5H4, Sprinco Green or Geissele Super42.
And then complain about the barrel being overgassed.
Well no shit.
Fix it till it won’t run. I’d bet this is how we ended up with reamed out ports.
Leonidas24
08-08-21, 14:53
There's probably not a discernible difference between a .071 and a .073 gas port.
Keep in mind that felt recoil is a sum of parts and not just a gas port size. So, barrel length and profile, gas port, BCG efficiency, gas tube interface, buffer system, and overall weight of the rifle.
I agree to an extent. But, one could at that point argue there's not a discernible difference between .073 and .076, but we know that there's a big difference in felt recoil and gun operating characteristics going from .076 to .071 at the midlength gas port position, or at least that I've been able to notice.
There is a notable difference in function with a .002/.003 port size change.
It's what we consider one "step" in port size.
Two steps is big difference, and is completely obvious even to those not paying attention while shooting.
I agree to an extent. But, one could at that point argue there's not a discernible difference between .073 and .076, but we know that there's a big difference in felt recoil and gun operating characteristics going from .076 to .071 at the midlength gas port position, or at least that I've been able to notice.
Or, be confident that when you buy a top shelf rifle, the engineers know something, and just shoot it.
Colt uses H2 buffers in their M4A1
I have one and it also gauged at 0.076"...
I might have to take off my gas block to check, but I don't have any pin gauges. If it's a 0.076" gas port, that seems like a recent change, but even so it's still something like an informal midlength "standard" for 16" barrel. That's what just about every high end manufacturer use, like Sionics, BCM, Criterion, SOLGW, etc. The only major manufacturers that went smaller were DD with 0.073" and Colt with 0.071".
I might have to take off my gas block to check, but I don't have any pin gauges. If it's a 0.076" gas port, that seems like a recent change, but even so it's still something like an informal midlength "standard" for 16" barrel. That's what just about every high end manufacturer use, like Sionics, BCM, Criterion, SOLGW, etc. The only major manufacturers that went smaller were DD with 0.073" and Colt with 0.071".
Several of the manufacturers you listed go smaller than .076" on a 16" bbl.
Several of the manufacturers you listed go smaller than .076" on a 16" bbl.
Which ones? Has anyone compiled a list of 16” midlength port sizes by manufacturer?
Colt uses H2 buffers in their M4A1
I’m well aware of that. I’m also aware that when the M4A1 had govt profile barrels, before we got upgraded to the newer heavier type, it came with H buffers. Would anybody care to guess which profile the DD V9 has?
Edit: the assholeness of this post was completely unintentional. I would make an awful diplomat.
I forgot to mention the type of muzzle device in the sum of parts.
Leonidas24
08-09-21, 06:54
Which ones? Has anyone compiled a list of 16” midlength port sizes by manufacturer?https://docs.google.com/spreadsheets/d/1tXunBDX5Gaz87BqxwNxDUlWNK9nEv-cZEQoLq2JXXrk/htmlview
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I’m well aware of that. I’m also aware that when the M4A1 had govt profile barrels, before we got upgraded to the newer heavier type, it came with H buffers. Would anybody care to guess which profile the DD V9 has?
Edit: the assholeness of this post was completely unintentional. I would make an awful diplomat.
We all have our days.
After testing different carbine buffers with 5.56 ammo in an 11.5 AR upper with an adjustable gas block, I found the H2 has softer recoil than the lighter buffers. I also found that the carbine, H and H2 buffers required the same gas setting for full lock back. As it has been commonly accepted that heavier buffer weights required larger gas ports, this came as a complete surprise.
I think there’s a range of weight that the gas drive works with.
Too light, and there’s not enough mass to retain enough momentum for the everything to fully cycle.
Too heavy and you have the same problem.
H2 and A5-2 seem to be the almost universal sweet spot.
We all have our days.
After testing different carbine buffers with 5.56 ammo in an 11.5 AR upper with an adjustable gas block, I found the H2 has softer recoil than the lighter buffers. I also found that the carbine, H and H2 buffers required the same gas setting for full lock back. As it has been commonly accepted that heavier buffer weights required larger gas ports, this came as a complete surprise.
I read your testing on that, and thanks for posting it. In my own testing, where I attempted to reproduce yours (and I believe Buford T Justice), I concluded that my click (3 clicks/turn) adjustable gas block really wasn’t very fine, and more often than not, a setting that ran one buffer would run pretty much whatever buffer. Which of course mimics your results, just with a different conclusion. Which was that my results were inconclusive, and the heavier buffer smoothed out the not-really-all-that-fine-tuned setting.
I did find on my gamer gun that my recovery between shots was faster when tuned to run .223 with a buffer filled with aluminum weights.
I intend to do some experimenting with gas port inserts or EZ Tune tubes at some point, so I’ll have numbers. Maybe I’ll finally put that DD Mk 18 barrel to use.
Several of the manufacturers you listed go smaller than .076" on a 16" bbl.
I checked the gas port spreadsheet and the manufacturers I listed all seem to go 0.076”. I feel like this is currently the “standard” for 16” midlengths since it gives reliable operation in all weather conditions.
Maybe my BCG has a better than usual gas seal as result of tolerance stacking. I think how gassy an rifle is depends on the individual rifle, even if all numbers on paper are the same because of production tolerances.
H2 and A5-2 seem to be the almost universal sweet spot.
Has 16” midlengths with H2 have any problems in cold weather? Wonder if this again depends on the individual even if all numbers on paper are the same.
Has 16” midlengths with H2 have any problems in cold weather? Wonder if this again depends on the individual even if all numbers on paper are the same.
I’d be willing to bet 3 doughnuts that your rifle will run proper brass cased ammo with an H2 buffer, if thats what you’re asking. It’d probably also run the A5H2 that Mistwolf was getting on about, and you’d even feel a small difference with that.
However, this: https://www.primaryarms.com/strike-industries-warhog-compensator-1-2x28 or this: https://www.primaryarms.com/surefire-procomp-muzzle-brake-1-2x28-procomp556-1-2-28 would probably do more. But then your friend will hate you. Then you’ll want a silencer. And in 10 months, your rifle will be super overgassed. So you’ll be ****ing with buffers again. And then you’ll get a BRT EZ Tune. But then you’ll want a SBR. Its a disease. But the same $3,000 could buy enough ammo and training to kick your friend’s ass all over the range, also.
As it has been commonly accepted that heavier buffer weights required larger gas ports, this came as a complete surprise.
I assume sarcasm?
And, many 16" barrels are technically under-gassed, if you point them straight down and fire a single round they won't lock back on the empty magazine.
Has 16” midlengths with H2 have any problems in cold weather? Wonder if this again depends on the individual even if all numbers on paper are the same.
There is nothing marginal about the gas drive with any 16” mid that I’m aware of.
All my midlength experience is with BCM and DD barrels.
The BCMs were complete uppers and cycled hard enough that they dented brass and beat up firing pin retainer pins. I ran those uppers up to A5-4 and they just seemed to recoil harder as the weight went up.
The DD barrels were rebuilds on Colt uppers, used new bolts and original carriers and were fine. I only ran them on A5-2 buffers.
And, many 16" barrels are technically under-gassed, if you point them straight down and fire a single round they won't lock back on the empty magazine.
Is it safe to shoot into dirt to perform that test?
I assume sarcasm?
And, many 16" barrels are technically under-gassed, if you point them straight down and fire a single round they won't lock back on the empty magazine.
I've never heard of this test before. It certainly has my curiosity.
I assume sarcasm?
Years ago, when I first started seriously looking into the technical side of ARs, the common advice to fix an over gassed AR was to use a heavier buffer. Another bit of common advice was to use the heaviest buffer that still allowed full function. So, I figured a heavier buffer would require a larger diameter gas port. To my surprise, that turned out to be a false assumption.
…Then you’ll want a silencer. And in 10 months, your rifle will be super overgassed. So you’ll be ****ing with buffers again.
Not if you know what you’re doing. Instead of messing around with buffers,
you’ll get a BRT EZ Tune.
Or a BRT suppressor barrel.
But then you’ll want a SBR. Its a disease. But the same $3,000 could buy enough ammo and training to kick your friend’s ass all over the range, also.
Just get the SBR, suppressor AND training. It’s where you’re gone end up anyway.
11.5" Carbine .071
14.5" Carbine .0625
16" Carbine .0625
16" Mid .076
Combined with A5H2 offers a wide performance envelope; unsurpassed or suppressed, dirty, dry, hot, cold.
Not the end all be all but proven, reliable, and predictable.
Years ago, when I first started seriously looking into the technical side of ARs, the common advice to fix an over gassed AR was to use a heavier buffer. Another bit of common advice was to use the heaviest buffer that still allowed full function. So, I figured a heavier buffer would require a larger diameter gas port. To my surprise, that turned out to be a false assumption.
I think that is mostly due to the fact most people don't think about what is actually going on from a physics point of view. If you have an over-sized gas port, you are introducing more energy into the system than required. A heavy buffer does not remove energy from the system, it just slows the bolt's acceleration and to a lesser extent, the final velocity, But the excess energy is still there.
Let's say the amount of energy is E
1/2 x Mh x Vl^2 = E = 1/2 x Ml x Vh^2
with:
Mh = heavy mass
Ml = light mass
Vh = velocity, high
Vl = velocity, low
Since the velocity is squared, it will dominate the equations, the relatively small change in mass will not make large changes in bolt velocity. Try putting a .5 kg mass at 6 m/s into the equation and see how much mass will be required to slow the velocity by 10%. (Hint, the answer is nearly 25%)
What a heavy buffer does is reduce the initial acceleration of the the bolt, which helps in keeping rims intact during extraction. So, if you are severely over gassed, heavier buffer may cure some of the symptoms, but the problem of excess energy is still there.
I think that is mostly due to the fact most people don't think about what is actually going on from a physics point of view. If you have an over-sized gas port, you are introducing more energy into the system than required. A heavy buffer does not remove energy from the system, it just slows the bolt's acceleration and to a lesser extent, the final velocity, But the excess energy is still there.
Let's say the amount of energy is E
1/2 x Mh x Vl^2 = E = 1/2 x Ml x Vh^2
with:
Mh = heavy mass
Ml = light mass
Vh = velocity, high
Vl = velocity, low
Since the velocity is squared, it will dominate the equations, the relatively small change in mass will not make large changes in bolt velocity. Try putting a .5 kg mass at 6 m/s into the equation and see how much mass will be required to slow the velocity by 10%. (Hint, the answer is nearly 25%)
What a heavy buffer does is reduce the initial acceleration of the the bolt, which helps in keeping rims intact during extraction. So, if you are severely over gassed, heavier buffer may cure some of the symptoms, but the problem of excess energy is still there.
After experimenting with different buffers and settings on an adjustable gas block, my conclusions match your statements of facts in the above. Further, I found when fitted with light buffers (carbine weight buffers), the AR has sharper felt recoil.
After experimenting with different buffers and settings on an adjustable gas block, my conclusions match your statements of facts in the above. Further, I found when fitted with light buffers (carbine weight buffers), the AR has sharper felt recoil.
. . . . H and H2 buffers required the same gas setting for full lock back. . . .
A rifle buffer with a standard M16 bolt carrier assembly has a mass of .4366 kg. Experimental data shows its velocity is around 6.375 m/s. So, we can assume that 8.872 joules is a good energy value for a properly gassed system.
We can adjust the energy input into the system with a adjustable gas block, so theoretically we can dial in exactly 8.872 joules worth of gas. So for the various buffer weight in a carbine buffer system, we get the following bolt velocities:
H3 - 6.353 m/s
H2 - 6.526 m/s
H - 6.687 m/s
STD - 6.911 m/s
The change in the velocity from standard to H3 is a mere 9% . . .
A rifle buffer with a standard M16 bolt carrier assembly has a mass of .4366 kg. Experimental data shows its velocity is around 6.375 m/s. So, we can assume that 8.872 joules is a good energy value for a properly gassed system.
We can adjust the energy input into the system with a adjustable gas block, so theoretically we can dial in exactly 8.872 joules worth of gas. So for the various buffer weight in a carbine buffer system, we get the following bolt velocities:
H3 - 6.353 m/s
H2 - 6.526 m/s
H - 6.687 m/s
STD - 6.911 m/s
The change in the velocity from standard to H3 is a mere 9% . . .
So, what I think I’m reading is…. If I have a high quality factory rifle, I can just shoot it?
(Suppressors not considered in this hypothetical)
So, what I think I’m reading is…. If I have a high quality factory rifle, I can just shoot it?
(Suppressors not considered in this hypothetical)
If you have a mediocre factory rifle you can probably just shoot it, and it will be okay.
I'm getting the feeling that even in good manufacturers, there's a range of tolerances so some rifles will feel more gassy than others even when paper numbers are identical.
We rarely disagree on technical aspects, but there may be an improper assumption here.
The assumption being that the gas system imparts constant Energy to the action.
I submit what the gas system actually does is impart constant Impulse and therefore constant Momentum to the action.
Impulse is right in the techical papers from Army BRL in the form of PSI-SEC, which through the piston area translates to Lbf-Sec, which converts to Momentum of the moving parts.
Adjusting the gas port size does change the Impulse, which we've been referring to for a while now as the "Gas Drive".
I think that is mostly due to the fact most people don't think about what is actually going on from a physics point of view. If you have an over-sized gas port, you are introducing more energy into the system than required. A heavy buffer does not remove energy from the system, it just slows the bolt's acceleration and to a lesser extent, the final velocity, But the excess energy is still there.
Let's say the amount of energy is E
1/2 x Mh x Vl^2 = E = 1/2 x Ml x Vh^2
with:
Mh = heavy mass
Ml = light mass
Vh = velocity, high
Vl = velocity, low
Since the velocity is squared, it will dominate the equations, the relatively small change in mass will not make large changes in bolt velocity. Try putting a .5 kg mass at 6 m/s into the equation and see how much mass will be required to slow the velocity by 10%. (Hint, the answer is nearly 25%)
What a heavy buffer does is reduce the initial acceleration of the the bolt, which helps in keeping rims intact during extraction. So, if you are severely over gassed, heavier buffer may cure some of the symptoms, but the problem of excess energy is still there.
A rifle buffer with a standard M16 bolt carrier assembly has a mass of .4366 kg. Experimental data shows its velocity is around 6.375 m/s. So, we can assume that 8.872 joules is a good energy value for a properly gassed system.
We can adjust the energy input into the system with a adjustable gas block, so theoretically we can dial in exactly 8.872 joules worth of gas. So for the various buffer weight in a carbine buffer system, we get the following bolt velocities:
H3 - 6.353 m/s
H2 - 6.526 m/s
H - 6.687 m/s
STD - 6.911 m/s
The change in the velocity from standard to H3 is a mere 9% . . .
We rarely disagree on technical aspects, but there may be an improper assumption here.
The assumption being that the gas system imparts constant Energy to the action.
I submit what the gas system actually does is impart constant Impulse and therefore constant Mlomentum to the action.
Impulse is right in the techical papers from Army BRL in the form of PSI-SEC, which through the piston area translates to Lbf-Sec, which converts to Momentum of the moving parts.
Adjusting the gas port size does change the Impulse, which we've been referring to for a while now as the "Gas Drive".
Assuming the same ammunition with the same propellant, the same rifle with its own quirks and the same ambient conditions, the energy is close enough to constant for this thumbnail sketch of what's going on, and explain why MistWolf did not see any gas adjustment difference between some lighter and heavier buffers.
Yes, you can breakdown the explanation in terms of impulse and momentum, and probably get more exact numbers, but it would be harder to follow and take longer.
I am reminded of this discussion: https://www.m4carbine.net/showthread.php?184697-Long-stroke-SureFire-Carrier&p=2776048#post2776048
In one of the threads on the LMT Enhanced Carrier it was proposed that the slightly delayed extraction allowed less energy to be dissipated in extraction. If a heavy buffer delays extraction ("helps in keeping rims intact during extraction") then less energy is used ripping an expanded case from the chamber, right?
I submit what the gas system actually does is impart constant Impulse and therefore constant Mlomentum to the action.
Impulse is right in the techical papers from Army BRL in the form of PSI-SEC, which through the piston area translates to Lbf-Sec, which converts to Momentum of the moving parts.It’s a fair distinction, but I’m not convinced of the mechanics based solely on someone’s choice of units. Do any of those papers actually describe a test in which they vary the carrier+buffer mass, measure the resulting carrier velocity, and check to see whether constant-energy or constant-impulse is a better fit to the data? Or at least present a reasonable simulation?
I don’t know which assumption is correct (if either), but here’s an argument in favor of constant-energy: the BCG vents the gas in the bolt-carrier chamber after the carrier moves a fixed distance (~ 0.3”) away from the bolt. This fact suggests to me that, for a given ammo and port size, a more-or-less fixed amount of work (force x distance) is done, and so the BCG/buffer starts it’s recoil with a fixed amount of kinetic energy.
Now implicit in the argument above is an assumption of constant force before venting. That’s not really true, but I suspect more true than the idea that the piston sees the entirety of the gas impulse come and go before venting.
This fact suggests to me that, for a given ammo and port size, a more-or-less fixed amount of work (force x distance) is done, and so the BCG/buffer starts it’s recoil with a fixed amount of kinetic energy.
Kinetic energy is certainly lower for a heavier BCG/Buffer because velocity affects the calculation far more than mass and a heavier BCG/Buffer must travel slower. Momentum should be the same (or very close).
The main take-away for me personally is that the BCG and buffer mass have less effect on the system than I believed.
Andy
Kinetic energy is certainly lower for a heavier BCG/Buffer because velocity affects the calculation far more than mass and a heavier BCG/Buffer must travel slower. Momentum should be the same (or very close).
The main take-away for me personally is that the BCG and buffer mass have less effect on the system than I believed.
Andy
We know that the amount of energy/force doesn't change appreciably, but as you said, the velocity must indeed be slowed in order for the force to remain the same (or essentially the same). Doesn't this mean that carrier velocity is then noticeably reduced, increasing lock time?
Kinetic energy is certainly lower for a heavier BCG/Buffer because velocity affects the calculation far more than mass and a heavier BCG/Buffer must travel slower. Momentum should be the same (or very close).If it weren’t for the vents, I’d agree. For a given profile of pressure (and hence force) vs time, the acceleration and velocity are decreased in inverse proportion to the mass. Momentum is unchanged but kinetic energy is reduced.
But the vents change the picture because they cut off the pressure curve after the carrier has moved a fixed distance, not a fixed time. With a heavier, slower carrier/buffer, it takes longer for the vents to open, and that means the force acts over a longer interval of time. To some extent that makes up for the reduced acceleration.
With the simplest model, in which you apply a constant force over a fixed distance, it turns out that it’s the energy (rather than momentum) that’s unchanged when the mass is varied.
ETA: It’s _energy_ that matters when trying to compress a spring. So if MistWolf is correct in claiming that lock-back is independent of buffer mass, that suggests the initial kinetic energy of the carrier/buffer must also be independent of mass. If the kinetic energy were reduced by use of a heavier buffer, you’d expect to need more gas to obtain lock-back.
win&legend
09-15-21, 08:38
According to Daniels tech line, most of their 14 and 16" barrels are gassed to produce a 3 o'clock ejection on full powered ammo with an H1 buffer. (standard mass carrier's run 11ish oz). Depending on your application, that may be over gassed for reliability purposes.
I have found that NiB carriers / bolts with Wilson Combat's one piece 4 coil gas rings really create 1. good gas seal to fully utilize the available gas pressure 2. significantly reduce the amount of friction buildup with fouling, so less mass and drive is actually needed to achieve the same reliability as a phosphate carrier with more mass.
I run a hybrid setup with an 8.5oz low mass carrier (NiB) and JP SCS set for H1 weight and their 85% black spring with the gassing tuned for 3 o'clock ejection. Very light and short recoil impulse, but also has been 100% reliable even when heavily fouled without cleaning. I ran 1,500 rounds before cleaning. Doing it again but only at 500 rounds on this interval.
Slightly more buffer mass gives a little extra dead blow over carbine buffer obviously. The JP SCS is another key element, because you reduce the spring friction against the buffer tube which is probably more than most people realize. This also has a small benefit on muzzle velocity as the less gas you need to run the system, the less pressure drop you get as the bullet travels down the remaining length of barrel until it exits. Not huge, but 10 to 20 FPS is still 10 to 20 FPS. Also others note far less fouling than heavily gassed systems, so in general, it stays notably cleaner for longer and is far less prone to changes in friction over that interval.
Some times more is not better for reliability. It's about efficiency. And reducing recoil is entirely about gas port pressure and reducing friction to minimize the required energy. Gas pressure is the energy transfer. Buffer masses and springs do not change recoil impulse energy, they only affect carrier speed, BCG energy storage potential when going back into battery and ultimately the shape of the recoil impulse wave form. Slower speed, you get more of a rainbow wave form, faster speed and you get more of a mountain top wave form over a shorter time interval.
If you want to actually reduce recoil, you need to reduce the source of the energy, which is at the gas pressure. Then balance the system around that energy level. I've found a short recoil impulse (2 to 3 o'clock ejection) with a lower mass / low friction system to really be the ideal balance for a fighting gun. Not sure if it would remain reliable in a sandy environment, but given I'm a civilian in the US around the Great Lakes region, not really a concern so I can reap the benefits of this system.
However I suspect it most likely would still remain reliable even in dusty conditions due to the significant reduction in friction over more common BCG configurations. Also you can always douse it with SLIP2000 or other high performance oils. Even with external fouling (dust, dirt etc.), the US Military found that more oil was still better than light or no oil, at least with phosphate carriers.
Interesting discussion. Also running an adjustable gas block, 100% reliability and lockback on empty even w PMC/American eagle 223. Full weight BCG but substituted aluminum weights in the A5 buffer so is it a minus something buffer?
Thinking of trying a Wolff reduced power rifle length action spring to reduce dot movement during rapid fire. $20 experiment.
Mark
I run a hybrid setup with an 8.5oz low mass carrier (NiB) and JP SCS set for H1 weight and their 85% black spring with the gassing tuned for 3 o'clock ejection. Very light and short recoil impulse, but also has been 100% reliable even when heavily fouled without cleaning. I ran 1,500 rounds before cleaning. Doing it again but only at 500 rounds on this interval.
Why the reduced power spring? Any failures to strip the first round from dirty magazines?
if MistWolf is correct in claiming that lock-back is independent of buffer mass, that suggests the initial kinetic energy of the carrier/buffer must also be independent of mass. If the kinetic energy were reduced by use of a heavier buffer, you’d expect to need more gas to obtain lock-back.
Let's keep in mind that we're talking buffers that work within the span of operation. Go too light or too heavy and function will be affected. There are three legs to AR function and all three must be in balance-
- Gas drive
- Reciprocating mass
- Spring rate
Change one of those legs too much and it throws the system out of balance. It changes the timing. However, there is room for small variations while maintaining the span of operation. For example, buffers weights ranging from about 3.0 oz to 5.4 are within that span of operation using 5.56 spec ammo. Venture too far outside that range and you start having problems. (While ARs will function reliably with 3.0 oz buffers, a 3.0 oz buffer is too light. It gives sharper recoil and it's affects on the shooter accumulate with each shot. It also adds time needed to get the AR back on target.)
Timing is very important to reliable feeding. If the carrier is moving too slow or with too little momentum, the round being stripped from the magazine will bobble. It will nose up and jam in the action. The round has to be stripped with enough speed and authority it doesn't have time to bobble. If the carrier speed is too high or there's too much momentum, the carrier will bounce. While carrier bounce may not have an impact on function in semi-auto, it adds to the time required for the AR to get back on target.
While I found the buffers tested didn't require different gas settings, it's important to understand my testing was confined to buffers falling between Carbine and Rifle/A5H2 in weight.
My last 3 have gauged out at 0.076"
A friend pin gauged his DDM4 16" barrel and it was between 0.072" and 0.073", which checks out with what DD told me in an email. Curious about the 0.076" you gauged, are they 16" midlength government profile in 5.56? Wonder if their S2W or LW barrels would have different gas port diameters, or perhaps you had a different caliber. According to DD their 14.5" midlength is 0.076", and it would baffle me if DD drills their gas port size wrong by mistake.
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