View Full Version : Theoretical advantage of A5 buffer system?
What is the theoretical advantage of the A5 buffer system over a carbine buffer system with a flat-wire spring?
Use of flat-wire allows for a longer spring with a lower spring constant which should be able to match the A5 force curve unless the latter used an even longer flat-wire spring.
The A5 buffer itself is longer, uses four weights instead of three, and includes a bias spring. Perhaps having more pieces provides an improved dead-blow effect even when the mass is similar, e.g. H2 and A5H1. I suppose the bias spring makes the system more consistent, e.g. between muzzle up and down, but does it do more? Does the longer body itself contribute to smoother cycling, such as by being less prone to pitch or yaw?
The flat wire spring variable throws me for a loop. I've no idea what that is/does.
The A5 notion is that you get the Rifle buffer weight/spring with it's longer compression position in an RE almost as short as the carbine.
A flat wire spring can provide the "longer compression position" (lower spring constant, flatter force curve) of a standard rifle spring in less space, i.e. a carbine extension. I think there's more to the A5 than that however. If it were merely mass and spring constant it should be possible to duplicate that (the common A5 setup) with an H3 and the right strength of flat-wire spring.
You've got the right idea.
There are however at least two mega threads covering the A5 system here and a quick search should reveal a goldmine of information on it.
The A5 buffer itself is longer, uses four weights instead of three, and includes a bias spring. Perhaps having more pieces provides an improved dead-blow effect even when the mass is similar, e.g. H2 and A5H1. I suppose the bias spring makes the system more consistent, e.g. between muzzle up and down, but does it do more? Does the longer body itself contribute to smoother cycling, such as by being less prone to pitch or yaw?
I run a5h2 and tubbs flatwire springs in my 10.3,y 12.5 and my 16. I really like the setup. It's also one of those things that you need to try for yourself.
A flat wire spring can provide the "longer compression position" (lower spring constant, flatter force curve) of a standard rifle spring in less space, i.e. a carbine extension. I think there's more to the A5 than that however. If it were merely mass and spring constant it should be possible to duplicate that (the common A5 setup) with an H3 and the right strength of flat-wire spring.
Rsilvers best duplicated the A5 or Rifle system with the carbine standard spring and H2 buffer. I forget his measurements, but the flat spring wasn't part of his testing. I forget exactly how close it matched the A5/rifle.
Clint, I shall read more.
corey4, do you use the standard length Tubb spring?
markm, is that on this forum?
markm, is that on this forum?
Yes, sir. It's a few years back. "rsilvers" was the guy (formerly of Advanced Armament)
Thanks, I'll search for it.
I found this from Clint, supporting my conjecture.
One big advantage of the A5 is the 4 weights it contains vs the 3 in the carbine. For reference, the rifle buffer contains 5+ weights and disks.
The internal moving weights are what make a buffer a BUFFER instead of just a spring guide and bump stop.
A stainless steel body is heavier than aluminum, but it can't have more moving weights inside than 3 tungsten, and therefore can't be a better buffer.
markm, did rsilvers throw the H6 into the mix? I know it’s an odd option, but it was the choice of the Army.
Does the H6 use more than three buffer weights and disks? I haven't been able to confirm this. If it does and one can figure out how to add a bias spring it would be very interesting to see a test of that modified buffer with a flatwire spring in a carbine RE versus the A5 system.
https://www.m4carbine.net/showthread.php?217262-H6-Buffer
The biasing spring doesn’t do anything as there is recoil happening before the bolt starts to unlock that will set the weights to the front of the buffer.
It was not put in the A5 buffer for any functional purpose.
The A5 has an actual and well documented advantage over the carbine length RE/buffer/action spring for ARs running an adjustable stock. The only real disadvantage are cost and availability.
Even cost is a wash compared to systems using proprietary springs, buffer weights, etc.
Andy
For a new carbine the A5 system seems like the obvious choice for only $50 extra, assuming you can find one right now.
In other applications less so. Consider a pistol with the Law folding adapter. The adapter and its extension plug already add length and mass and the A5 would be more of the same. The Law plug could require the use of a lighter buffer which might not be as effective as the popular A5H2.
Yes, sir. It's a few years back. "rsilvers" was the guy (formerly of Advanced Armament)
I still haven't found that but I did find something else of interest.
The flat wire buffer spring concept makes no sense... Flat wire springs are normally good because the spring won't come as close to solid height - but that benefit is when you have the room for a larger OD or a smaller ID. On the AR, the buffer tube and buffer constrain the spring so that a flat-wire version is merely missing some material and hence would be higher stress than a round-wire spring. I would expect it to be more likely to break.
I think rsilvers had it completely wrong about flat-wire springs seeing more stress and hence being more likely to break. In fact, given two springs of equal strength, one with a flattened profile and the other round, the flat one will see less stress and be more durable.
Bow makers have known this for many thousands of years.
Five_Point_Five_Six
08-01-20, 17:55
For a new carbine the A5 system seems like the obvious choice for only $50 extra, assuming you can find one right now.
In other applications less so. Consider a pistol with the Law folding adapter. The adapter and its extension plug already add length and mass and the A5 would be more of the same. The Law plug could require the use of a lighter buffer which might not be as effective as the popular A5H2.
There are no issues using the A5 in conjunction with a Law folder on an AR pistol or SBR, in fact shorties are where the A5 really shines in my opinion. Dropping down to the next buffer to accommodate the added weight of the BCG extension is something that is only gonna be required if your setup was already running on the ragged edge of reliability. If you're right in the middle of the reliability window in terms of gas port, buffer and spring combo, and ammo, which is where I prefer mine to be, adding the Law folder with BCG extension won't cause it to start malfunctioning unless you were borderline over sprung, over buffered, and/or using weak ammo before hand.
BufordTJustice
08-02-20, 01:08
The biasing spring doesn’t do anything as there is recoil happening before the bolt starts to unlock that will set the weights to the front of the buffer.
It was not put in the A5 buffer for any functional purpose.
You have constructed a post wherein every single sentence is 100% incorrect.
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You have constructed a post wherein every single sentence is 100% incorrect.
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Ok then.
Clint, I shall read more.
corey4, do you use the standard length Tubb spring?
markm, is that on this forum?
i use the ar15 version: http://www.davidtubb.com/ar15-bufferspring and i use the 308 version for my 308s.
You have constructed a post wherein every single sentence is 100% incorrect.
Lol! I did pop the spring out of some of my A5 buffers. I didn't notice a difference, but I left any new builds with the spring intact.
BufordTJustice
08-03-20, 11:07
Lol! I did pop the spring out of some of my A5 buffers. I didn't notice a difference, but I left any new builds with the spring intact.
It’s a rate stabilizing spring. It also ensures that during the first 1/8” to 1/4” of carrier movement (when unlocking occurs) that the stack of internal weights applies full mass to the rear of the carrier. It turns every milspec carrier into one of those fancy weighted carriers, but with no downside.
Now, shooting from a stable position and not a lot of up-angle and it might not make a ton of difference in terms of feel.
My brass always stacks tighter on the ground when I have the spring in place. I’ve tried it both ways as well.
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davidjinks
08-03-20, 11:13
Theoretically it’s supposed to give you less felt recoil ala rifle type buffer system.
Just as markm stated below.
What is the theoretical advantage of the A5 buffer system over a carbine buffer system with a flat-wire spring?
Use of flat-wire allows for a longer spring with a lower spring constant which should be able to match the A5 force curve unless the latter used an even longer flat-wire spring.
The A5 buffer itself is longer, uses four weights instead of three, and includes a bias spring. Perhaps having more pieces provides an improved dead-blow effect even when the mass is similar, e.g. H2 and A5H1. I suppose the bias spring makes the system more consistent, e.g. between muzzle up and down, but does it do more? Does the longer body itself contribute to smoother cycling, such as by being less prone to pitch or yaw?
I never used the flat wire springs. But the A5H2 I used was pretty meh.
The flat wire spring variable throws me for a loop. I've no idea what that is/does.
The A5 notion is that you get the Rifle buffer weight/spring with it's longer compression position in an RE almost as short as the carbine.
This is what I currently use in all of my non-SBR rifles and they work well. For the SBR’s, they get the H3.
Rsilvers best duplicated the A5 or Rifle system with the carbine standard spring and H2 buffer. I forget his measurements, but the flat spring wasn't part of his testing. I forget exactly how close it matched the A5/rifle.
BufordTJustice, I read your entire thread about the A5 and LMT e-carrier and I have a question. Rather than necro-post I'll ask here. With the A5H4 and a standard rifle spring, and with the carbine aimed straight up, does it still easily strip the first round from a magazine when released with the BHO?
BufordTJustice
08-03-20, 16:45
BufordTJustice, I read your entire thread about the A5 and LMT e-carrier and I have a question. Rather than necro-post I'll ask here. With the A5H4 and a standard rifle spring, and with the carbine aimed straight up, does it still easily strip the first round from a magazine when released with the BHO?
Yes.
With the caveat that my guns all have a few K rounds through them. So they are broken in.
In a new upper, with a new parkerized carrier, you may have some issues with that specific test until you get a few hundred rounds. But only in the vertical position.
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Thanks. I would like to polish my carrier rails and sides of gas key the way you did. Is jouler's rouge by hand followed by a naked felt wheel at low speed, as described in post #97 of https://www.m4carbine.net/showthread.php?109353-LMT-Enhanced-Carrier-A5-system-BCM-14-5-quot-middy&p=1436559#post1436559 the method you recommend still?
Also, do you still use and recommend the V Seven cam pins?
BufordTJustice
08-03-20, 18:29
Thanks. I would like to polish my carrier rails and sides of gas key the way you did. Is jouler's rouge by hand followed by a naked felt wheel at low speed, as described in post #97 of https://www.m4carbine.net/showthread.php?109353-LMT-Enhanced-Carrier-A5-system-BCM-14-5-quot-middy&p=1436559#post1436559 the method you recommend still?
Also, do you still use and recommend the V Seven cam pins?
Yes and yes.
It’s just skipping the break in period. Wear acceleration. Used it on dozens of builds.
The V7 cam pin remains my favorite, but the Lantac pin (which I also use) is excellent as well. Preference, in slight degree, goes to V7, but both are excellent.
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What is the internal stroke of the A5 buffer, i.e. how far can the buffer weights move within the buffer body?
BufordTJustice
08-04-20, 10:44
What is the internal stroke of the A5 buffer, i.e. how far can the buffer weights move within the buffer body?
I haven’t measured.
I’m hazy but I want say Vltor made it slightly longer than a std carbine buffer. Don’t quote me.
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Botton line, they cost a little more and there is often upside and no downside. Zero downside that I've found. If you run a can, helps a lot. I dont know anything about the flatware either, I just use the spring they send with package. BCM makes one too.
There is a 5 position A5 or 7 position A5. I think they made the 5 for people that wanted their stock to go all the down on gun. So length could vary.
PB
By all accounts they are superior. I have no doubt of that. I was merely curious why that is so from a theoretical perspective. My questions have been answered as thoroughly as I could have hoped for. Thanks again.
nightchief
08-04-20, 11:46
https://www.arbuildjunkie.com/vltor-a5-buffer-system-overview/
This Q&A with the designer at Vltor talks about the A5 system development and theory behind its effectiveness.
I read that article before starting this thread. I did not find it satisfying. Emphasis is given to running a spring with a longer free length, but this can be achieved in the carbine extension using a flat wire spring. Emphasis is also given to the possibility of uncoupled mass above carbine H3 but the standard A5H2 is no heavier yet people find it superior. They did not spend much time talking about the biasing spring other than mentioning that it does not negate the deadblow effect on closing.
Emphasis is also given to the possibility of uncoupled mass above carbine H3 but the standard A5H2 is no heavier yet people find it superior.
This is the thing that made rsilvers's findings interesting. The H2 carbine, although lighter, mimicked the Rifle/A5H2 most closely. In other words direct weight comparisons between carbine and A5 don't translate due to the different springs.
I would love to find that post by rsilvers but I have as yet been unable to.
How does the A5 improve anything? The bcg moves the same distance. Over the years I've tried A5, flatwire springs, and heavy buffers. Nothing corrects issues like proper gas port. BRT gas tubes are a miracle.
I still run Tubbs springs, they just work.
Thanks for the kind words.
We believe proper gassing is the most important aspect.
A properly gassed gun will run a variety of buffers reliably, while no amount of heavy buffer will fully tame a grossly over gassed gun.
The A5 system does add a level of refinement and consistency vs conventional carbine buffer system.
How does the A5 improve anything? The bcg moves the same distance. Over the years I've tried A5, flatwire springs, and heavy buffers. Nothing corrects issues like proper gas port. BRT gas tubes are a miracle.
I still run Tubbs springs, they just work.
pointblank4445
08-04-20, 21:06
This is the thing that made rsilvers's findings interesting. The H2 carbine, although lighter, mimicked the Rifle/A5H2 most closely. In other words direct weight comparisons between carbine and A5 don't translate due to the different springs.
Don't suppose you know what would be the ideal flavor of A5 (has to be H0 or H1...cause anything heavier won't work) for an upper that won't run anything heavier than an H1 carbine and milspec carbine spring?
Don't suppose you know what would be the ideal flavor of A5 (has to be H0 or H1...cause anything heavier won't work) for an upper that won't run anything heavier than an H1 carbine and milspec carbine spring?
It's not that simple! I'm still trying to wrap my head around this observation.
When using the LMT e-carrier, Vltor A5 system, tubbs flat wire AR10 spring, and an SLR gas block, using several verified 5.56 NATO chambers, A5H0 buffer did not permit a smaller gas block "port" adjustment than the A5H4 buffer. In fact, on my suppressed 11.5" Sionics RGP and BRT 16" OPTIMUM intermediate gas barrel with the above setup the A5H4 permitted a smaller gas port setting on the gas block than the A5H0 or any of the other buffer weights (I tried all of them on all of my uppers, suppressed and unsuppressed). Yes, you read that right.
The A5H4 permitted me to run less gas than the A5H0.
I appreciate the few posts above showing lots of experimentation, but there is more going on here. Period.
I’m an admitted A5 fanboy. I’m currently liking the ‘amphibian’ setup using a kynshot RB5007 hydraulic buffer (endorsed by no less than Kyle Lamb), an A5 length tube, and Tubbs flat wire 300BLK or 556 flat wire spring. Very smooth setup.
https://www.kyntec.com/product/rb5007-kynshot-for-ar-9mm-application-12/
I’m an admitted A5 fanboy. I’m currently liking the ‘amphibian’ setup using a kynshot RB5007 hydraulic buffer (endorsed by no less than Kyle Lamb), an A5 length tube, and Tubbs flat wire 300BLK or 556 flat wire spring. Very smooth setup.
https://www.kyntec.com/product/rb5007-kynshot-for-ar-9mm-application-12/
I wonder if running a regular rifle spring vs the flatwire would equal the results.
The additional cost of the buffer has kept me away from trying it out. The A5 system by itself is already very good.
To put it simply, the overall gas impulse goes toward two things.
1) accelerating the moving mass
2) overcoming friction forces during extraction
In general, adding mass reduces acceleration and peak speed of the moving mass.
HOWEVER, those extraction related friction forces decrease with time as bore pressure and temperature drop.
IF increased mass delays extraction enough to reduce that friction, the saved energy is used to accelerate the mass to normal speeds.
It's not that simple! I'm still trying to wrap my head around this observation.
To get started, you can build a new lower using the longer receiver extension.
A spacer (such as the Colt 9mm spacer), rifle spring and CAR type buffer can be used after verifying proper travel.
This provides some benefit from the rifle spring and allows a future upgrade path the an actual A5 buffer in the future.
I wonder if running a regular rifle spring vs the flatwire would equal the results.
The additional cost of the buffer has kept me away from trying it out. The A5 system by itself is already very good.
I should clarify, I do use the A5H2 buffer. My comment was about combining the Kynshot buffer with the A5 tube and rifle spring.
BufordTJustice
08-05-20, 16:39
To put it simply, the overall gas impulse goes toward two things.
1) accelerating the moving mass
2) overcoming friction forces during extraction
In general, adding mass reduces acceleration and peak speed of the moving mass.
HOWEVER, those extraction related friction forces decrease with time as bore pressure and temperature drop.
IF increased mass delays extraction enough to reduce that friction, the saved energy is used to accelerate the mass to normal speeds.
Clint, you nailed it.
If the extraction is delayed until case obturation has largely subsided, there is more energy left in the overall energy budget to contribute to accelerating the carrier/buffer mass to the rear.
I’ve actually experimented with a custom 9.5oz A5 stainless buffer and it functioned just as well as the A5H2 and A5H4 through your OPTIMUM 16” Intermediate Gas barrel (which is already properly gassed), THROUGH an SLR Ti AGB with about 50% restriction.... at the exact same setting.
That is nearly a doubling of buffer mass. And it STILL locked back on empty with no shoulder purchase on XM193 and my sh*tty busted aluminum mag with dented feed lips that I use for just such a test (lock back). That was 62F in the indoor range that day.
As you said, there’s plenty of energy in the system to gas the gun properly AND have more than enough margin for operation.
The fact that your barrels come with properly cut chambers and leads/throats sure does help accomplish that. [emoji106][emoji41]
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