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Thread: Tuning ARs with different buffers and buffer springs?

  1. #1

    Tuning ARs with different buffers and buffer springs?

    The gas system of the AR is controlled to my knowledge by several components:

    The ammo generates a certain amount of PSI.
    The size of the gas port in the barrel is open to allow a certain amount of gas back.
    The gas block may impact gas?? Or only if itís an adjustable gas block?
    The length of the gas tube controls the speed of the gas.
    The weight of the bolt carrier slows down the gas.
    The weight of the buffer slows down the gas.
    The flexibility and length of the buffer spring slows down the gas.

    Of those, the easiest to modify are the buffer and the buffer spring. For an enthusiast who has several ARs, it seems cost reasonable to buy one of each buffer and buffer spring and do some testing.

    And then use the combination that results in the ďbestĒ outcome.

    My question is, what is the best outcome and how do you know you achieved it? Of course reliability is important, the most important, because if the gun doesnít feed, nothing else matters. Recoil might be better controlled or smoother with a better setup. But does that impact reliability?

    I assume the more forcefully the buffer moves, the more reliable. Since unreliability likely occurs when thereís not enough gas to cycle rhe bolt forcefully enough to extract the round or maybe doesnít move the bolt carrier back enough in the upper to collect the next round from the magazine.

    Recoil is likely reduced if you have a heavier buffer, heavier buffer spring, longer gas tube, smaller gas port, heavier bolt carrier, because the system is moving less forcefully.

    Does this mean thereís an inverse relationship between reliability and smoothness of recoil? Such that adding one unit of reliability makes it one unit of being less controllable?

    However, reliability is binary. Either the gun cycles each time or it doesnít. You wouldnít get benefit adding more gas once itís 100% reliable. Or 99.999%.

    If so, then it seems like the best path would be to identify the minimum acceptable reliability and adding a fudge factor to it. That should give the optimal recoil impulse without sacrificing reliability.

    In other words, if we have a combination of every buffer and buffer spring, start off with the heaviest buffer and heaviest buffer spring. The gun is likely not reliable. Then reduce the weights and keep testing until itís reliable. Then reduce weights one more time as a safety factor because the real world can kick you in the ass and would rather err on more forceful gas system than less.

    In theory that may work. What I donít know is how to effectively mix and match buffers and buffer springs. Do I start with heaviest of each and reduce by one of each? In other words does a medium buffer with medium buffer spring work the same as a heavy buffer with a light spring or a light buffer with a heavy spring? How does the combination impact it?

    I assume high level competition gamers do something like this? Anyone have experience? Even if I never do it, this was a fun thought experiment to teach me more about the workings of the carbine.
    Last edited by Sanch; 01-19-2022 at 11:56 AM.

  2. #2
    From personal experience tuning guns and sometimes competing with them, my first thought is that the most recoil reduction is going to be achieved by putting a really aggressive muzzle brake or compensator on the gun. The sort of mean muzzle device that makes people not want to stand next to you. As long as you don't have a pin/weld barrel, you can easily change out muzzle devices until you get one that works for you. Most of the buffer system/gas system changes are a lot more subtle. Also, unlike messing about with the gas system, you're not going to negatively impact reliability with a muzzle brake.

    Ok, easy answer of "Just put a big ol' 'Fuck off' brake on it and call it a day" has been said, on to the reciprocating mass and springs.

    Gas system length controls pressure in the gas system. A longer gas system (e.g. rifle) has less pressure than a shorter one.

    Adjustable gas blocks (or a smaller gas port) control the volume of gas in the system, but not the pressure. Or not the pressure entirely. Basically, what I'm getting at is that you can't use an adjustable gas block to make a carbine gas system feel entirely like a rifle gas system. If you're picky and can focus on it enough to care that is.

    If you want to start tuning, muzzle brake + adjustable gas block (AGB) will let you get started. The AGB is key, because that's the only way you can actually adjust the force that gets the carrier/buffer moving. I always think about recoil sources when trying to tune:

    1. Newton's 3rd law and the bullet that you shot at the target.
    2. Gas coming out the front of the barrel
    3. Bolt + carrier + buffer stopping moving rearward at the end of its travel
    4. Bolt + carrier + buffer stopping moving forward when it chambers a new round

    Our muzzle brake is going to help out with 2 by putting some of it to work for us instead of against us.

    All of the gas system and mass tuning is for 3 and 4. Once we cut down the gas pressure with the AGB, we're going to run into reliability problems. Extreme case, gun doesn't lockback (or doesn't cycle at all). So, we'd want to reduce the weight the (reduced) force has to move so our gun works again. Here's where reducing the buffer and carrier mass comes into play. This can get pretty extreme with titanium or aluminum carriers and empty buffers. Also reduced power springs, since that's less force to overcome, and less force for source 4.

    So, if you wanted the lightest, softest shooting rifle, you'd put a giant comp on it, have a rifle-length gas system, adjustable gas block, low mass carrier, low mass buffer, weakest buffer spring you could find that it would still run, tune the gas down to the bare minimum. You'd have to settle on one kind of ammo, keep it very lubed, but it would shoot like a laser and the sights would barely move.

    Does that help?

  3. #3
    Another thing that I have not extensively tested but just (IMO) makes sense is dwell time. And (IMO) the carbine length system doesn't really make sense with a 16" barrel. I am not totally clear on the history, but I believe the FSB and port got moved way back there to accommodate the 11.5" barrels, and that gas port location leaves a lot of travel (ETA: in a 16" barrel) for the bullet before it gets out and vents the gas.

    The few 16" carbine guns I have had just seemed harsh and I no longer have any in 5.56 (not like I have a bunch of guns), my primary 16" gun is mid-length. I also have an 18" gun that is rifle length, and it is pretty sweet (and since starting three gun, the one I shoot the most).

    So I agree with your thoughts about having some buffers to experiment with, but if you are starting with a 16" carbine gas system and you want it to be smoother, you might consider another barrel and gas tube (not really all that expensive).

  4. #4
    Quote Originally Posted by Sanch View Post
    In theory that may work. What I donít know is how to effectively mix and match buffers and buffer springs. Do I start with heaviest of each and reduce by one of each? In other words does a medium buffer with medium buffer spring work the same as a heavy buffer with a light spring or a light buffer with a heavy spring? How does the combination impact it?

    I assume high level competition gamers do something like this? Anyone have experience? Even if I never do it, this was a fun thought experiment to teach me more about the workings of the carbine.
    Here are the buffer weights and composition:

    Carbine Buffer (Avg 3.0 oz) - 3 Steel Weights

    Heavy (H) Buffer/AKA H1 Buffer (Avg 3.8 oz) - 1 Tungsten + 2 Steel Weights

    H2 Buffer (Avg 4.7 oz) - 2 Tungsten + 1 Steel Weights

    H3 Buffer (Avg 5.6 oz) - 3 Tungsten weights

    If you have extra weights you can build you own buffers. I mainly use KAK Industries weights and buffer parts, except for tungsten weights which I usually source from TungstenMan. I have H - H3 weights in my range bag and when I decide which weight buffer works best, I can easily convert the carbine buffer that comes with most carbine tube sets to that weight. After you've done a couple you have kind of a self-perpetuating supply of weights - except tungsten. Then same weights work on rifles. When I modify a carbine buffer I use a metal stamp to mark what it is. Until I got my stamp set I used different color buffer noses.

    I choose the buffer weight by function and feel paying less attention to ejection pattern than other folks may.

    Kind of a fun way to do it.

    A5 Buffers: The A5 system was reportedly developed by Vltor to enable a collapsible stock to be put on M16 rifles. The A5 buffers are a bit longer than the carbine buffers - 4inches versus 31/4 inches - and requires an A5 tube and a rifle buffer spring. These can be sourced from Vltor, BCM and Magpul. They are another way to smooth out the recoil and operating impulses. REgardeless of what system you are using, the BCG travels less than 4 inches. The springs compress same amount regardless of what buffer tube and spring you are using. The longer rifle spring has more length and more coils to do the work, so it has less of a differential between the unloaded and loaded states. This allows for smoother compression and extension, so they say.

    A5H0 (Avg 3.8 oz) - 4 steel

    A5H1 (Avg 4.56oz) - 1 tungsten, 3 steel

    A5H2 (Avg 5.33oz) - 2 tungsten, 2 steel

    A5H3: (Avg 6.08oz) - 3 tungsten, 1 steel

    A5H4: (Avg 6.83oz) - 4 tungsten, 0 steel

    Have fun!
    Adding nothing to the conversation since 2015....

  5. #5
    Quote Originally Posted by jbrimlow View Post

    So, if you wanted the lightest, softest shooting rifle, you'd put a giant comp on it, have a rifle-length gas system, adjustable gas block, low mass carrier, low mass buffer, weakest buffer spring you could find that it would still run, tune the gas down to the bare minimum. You'd have to settle on one kind of ammo, keep it very lubed, but it would shoot like a laser and the sights would barely move.
    I always assumed increasing the weight of the bolt carrier, buffer, and buffer spring would reduce the felt recoil. An inverse relationship. Because the energy causing the recoil gets absorbed by the heavier buffer/BC system and instead of as much energy going back into your shoulder and causing the muzzle to shift, the energy goes into trying to move the heavier buffer/BC/spring.

    I think youíre approaching it from a different anglet, which is you want to reduce as much gas as possible coming back into the gun, by having longer gas tube and a gas block that bleeds some of the pressure externally, instead of directed it all back into the gunÖ but by virtue of doing that, thereís not enough gas to cycle a regular bolt carrier/buffer/spring so you use the lightest buffer/carrier/spring possible which the significantly reduced pressure can still cycle?

    I think we both might be correct? But in my example Iím not messing with the gas block nor the gas tube nor muzzle device, Iím keeping those standard.

  6. #6
    Quote Originally Posted by Dan Lehr View Post
    when I decide which weight buffer works best, I can easily convert the carbine buffer that comes with most carbine tube sets to that weight. After you've done a couple you have kind of a self-perpetuating supply of weights - except tungsten. Then same weights work on rifles. When I modify a carbine buffer I use a metal stamp to mark what it is. Until I got my stamp set I used different color buffer noses.

    Have fun!
    Whoa! You can take apart a standard carbine buffer and modify the internal weights to make your own H-style buffers? I never looked closely enough to see how they come apart and never considered it! The prices on H2 and H3 buffers is insane compared to a standard buffer and I doubt the tungsten weights are that expensive.

  7. #7
    Quote Originally Posted by Sanch View Post
    Whoa! You can take apart a standard carbine buffer and modify the internal weights to make your own H-style buffers? I never looked closely enough to see how they come apart and never considered it! The prices on H2 and H3 buffers is insane compared to a standard buffer and I doubt the tungsten weights are that expensive.
    I was happy to learn this as well!

  8. #8
    Quote Originally Posted by Sanch View Post
    Whoa! You can take apart a standard carbine buffer and modify the internal weights to make your own H-style buffers? I never looked closely enough to see how they come apart and never considered it! The prices on H2 and H3 buffers is insane compared to a standard buffer and I doubt the tungsten weights are that expensive.
    Scroll down this page: https://www.kakindustry.com/ar-15-pa...ubes-and-parts

    I generally buy carbine buffer tube sets for my builds so that I get a donor buffer as well. I look for them on sale and buy several at a time.
    Adding nothing to the conversation since 2015....

  9. #9
    You can kinda tune how it feels with buffers but outside of mitigating bolt bounce on a full auto, messing around with buffers is largely placebo and most of the upgrades people do are actually less reliable and not as easy to shoot as the parts they replaced.

    I have done quite a bit of testing with different buffer setups, different shooters (good ones), and I will not so humbly preemptively say most everyone is wrong and even more people donít truly understand how the AR works.

    But ARs are very tolerant of buffer and spring variations, and buffers and springs are easily futzed with without tools so they will always be one of the most upgraded parts on the AR.

    Stick with the carbine/H/H2 for best results.

  10. #10
    This is a credible argument from Sprinco that explains why you should increase the weight of the buffer spring before you increase the weight of the buffer - https://www.sprinco.com/SPRINCO-DOCS...R%20Tuning.pdf

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