Hey Brother, I had a rather lengthy technical post already typed, but the forum dumped it into oblivion. So I'm starting from scratch.....
Regarding the part in your post that I bolded, I have found the opposite. I have found that heavier buffers, when used with a quality spring (Springco White, Colt carbine or BCM carbine that isn't too worn and weak, etc.), actually INCREASE the reliability of the carbines in which they are used as long as the gas port is sized within reason. Specifically regarding 6920's, I have found that malfunctions with frangible training ammo (you know that 45gr bull-nosed sh*t ammo for using in the shoot house and steel pit) are actually reduced when using heavier H2 and H3 buffers and quality extractor springs (such as the Colt Gold, BCM, or Springco 4/5 coil).
I find that the BCG/buffer column seems to work most reliably when it is running slower (what would be equivalent to a lower cyclic rate). I have always found that a gun runs more smoothly when using a heavier buffer than a carbine or H buffer.
I conceptualize it like this: the weapon always has the same amount of gas to cycle the system, regardless of buffer weight or spring rate. Going to a heavier buffer, if spring rate is kept constant, means that it requires more energy to initially move the buffer and that the entire BCG/buffer column will accelerate more slowly and reach a slower peak rearward-speed than would a lighter buffer'd setup. Since the amount of the gas doesn't change, this means a heavier column moving more slowly when it impacts the rear of the Receiver Extension. Since all the acceleration of the BCG happens when the gas tube is still telescoped within the carrier's gas key, increasing buffer weight has the ability to slow this initial acceleration. Yes, this means more weight coming to a stop, but that is moving more slowly. This also means more time for the round stack to move up in the magazine when firing full auto.
My experience (and that of other users here) has supported this.
My use of Vltor's A5 system and specifically their heavier A5H3 and A5H4 buffers (6oz and 6.8oz, respectively) has further confirmed my thoughts. In fact, I have yet to connect my lower using the Vltor rifle spring and the A5H3 buffer to a 6920 and not have it work perfectly using all ammo (including frang).
My experiences have transitioned my thought process to one very similar to IG's. I no longer "worry" about how heavy the buffer is, I am much more concerned that it is too light. Ammo reliability is highest in the A5 system (in my experience), which uses the heaviest buffers of all and a rifle spring. The Springco White is the closest you can get to a rifle spring in a carbine RE. I have never been able to take the same lower with the same spring and buffer and have it work 100% on a Colt SBR suppressed and unsuppressed, a std 6920 non-suppressed, DD 16" middy, BCM 14.5" middy, BCM 16" middy, Colt 20" HBAR, and an 18" rifle-gas upper non-suppressed before using the Vltor A5 system (and, in that case, an A5H4 6.8oz buffer).
Are there some guns that MUST have lighter buffers? Yes, like SR15's and some LMT 14.5" & 16" carbines. But most I have found to benefit from H2's and H3's. I suggest doing some small-scale experiments using H2's and H3's and a quality carbine spring...I think that you'll find that the smooth recoil stroke will surprise you.
Caveat: I have found that some guns, with absolutely hogged-out gas ports can exhibit MORE recoil using an H2 or H3 buffer, in which case this is indeed a bandaid solution (and the solution is to get a barrel that doesn't have a gas port the size of fifty-cent hooker's you-know-what)... but those have always been problem uppers (that won't run with std GI mag's with a green follower at all)....so I write that problem off as a separate issue altogether.

Originally Posted by
glockshooter
IG you are obviously a very knowledgable person on this weapon system and I appreciate your input. I also have a fair amount of experience maintaining and building rifles. Nothing like you have over the years, but not a small amount either. I have the same appreciation for a well built weapon as you do. I was personally responsible for transitioning my department away from Bushmaster SBRs and carbines to DD SBRs and Colt 6920s. I am also responsible for maintaining approximately 300 rifles. I say all of that just so you know I'm not a nut job just trying to bust your balls.
I am well versed in all the things listed in that post and I understand how they work in conjunction with the other. I guess my curiosity comes from the use of H3, 9mm, ST-whatever buffer and springs. They are in not way necessary for the rifle to work properly and in some cases can effect reliability by slowing the BCG down to much. I'm just not sure why such heavy buffers (not really referring to H or even H2 in SBRs) are used. There seems to be more downsides than upsides. The reciprocating mass of a heavier buffer and FA BCGs are going to adversely effect the recoil impulse and slow down your ability to take quick shots and again can in some cases be to heavy for your rifle to be reliable with a range of ammo.
Last edited by BufordTJustice; 02-26-14 at 13:59.
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