Intermediate length gas system

[MistWolf]

If I remember right, the H2 did not become standard in the M4a1 until the change to the heavier “SOCOM” barrel was made.

Correct. They were having problems with bolt bounce during full auto with the M4A1 which they solved by developing the H2 buffer. Chris Bartocci said in his video the bolt bounce resulted from the installation of the heavier SOCOM profile barrel.

When I tested the H buffer compared to the H2, recoil was softer with the H2. I used an 11.5" AR with an adjustable gas block with the intention of finding the "ultimate" buffer weight for suppressed and unsuppressed use. I expected to have to use a different setting going from the carbine buffer to the H2. I was surprised to learn that all three buffers required the same gas setting. The difference was in how the recoil felt. The heavier the the buffer, the softer the recoil. This was using using Federal XM193.

Adding a suppressor, of course, required a change in the gas setting. With the suppressor installed, the gas block was tuned until it was at the minimum setting required for ejection and reliable lockback. Using the same setting, removing the suppressor resulted in reliable ejection, but the action did not lock back, regardless of which of the three buffers was used. Again, the difference was in felt recoil.

Further testing with the A5H2 buffer (which is about the same weight as a rifle buffer) gave full function with even softer recoil than the three carbine buffers.

Changing reciprocating mass changes timing, something Lysander has preached for years. Change the timing too much and it has an impact on feed reliability.

You are correct. H buffer is in M4, H2 in M4A1, H2 or H3 in MK18.

That guy is just repeating internet mantra and doesn’t understand what the buffer is for and what the gas system does.

You caught me. When I went out to the desert to test gas settings, buffers & suppressors, I was just looking for a spot with cell service so I could post on TOS without being nagged by my wife to take out the trash.

[Disciple]

When I tested the H buffer compared to the H2, recoil was softer with the H2. I used an 11.5" AR with an adjustable gas block with the intention of finding the "ultimate" buffer weight for suppressed and unsuppressed use. I expected to have to use a different setting going from the carbine buffer to the H2. I was surprised to learn that all three buffers required the same gas setting.

BufordTJustice related a similar experience.

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.

[17K]

I’ve been thinking about the heavier buffer running with reduced gas when the A5H0 wouldn’t.

I’m thinking that the shorter, lighter puff of gas gets everything going about the same, but the heavier buffer has more momentum and gets all the way back. Kinda the same thing as a 147gr bullet not losing as much velocity as a 115gr in a short barreled 9mm.

I’d like to see that same setup tested loosely mounted to the shoulder and see what that does.

I’ve played around with buffers and was able to induce short stroking that way, the heavier the sprung stuff, the easier it is to do.

[Disciple]

I’ve played around with buffers and was able to induce short stroking that way, the heavier the sprung stuff, the easier it is to do.

I wonder how spring stiffness affects this. Did you experiment with that as well?

[17K]

I wonder how spring stiffness affects this. Did you experiment with that as well?

Not much. I always had stock A5 or Colt carbine springs.


I did have a Springco Blue in a 6920 for some ungodly reason. That gun lived outside and the spring rusted and quit working. Replaced with a stock one and back to 100%.

[1168]

I’ve experimented a good bit with springs, including on an intermediate gas system. What I have found is that increasing spring rate introduces stoppages to a functioning but lightly gassed gun. It also does not do as well as one might hope to tame a gassy beast. So there is little advantage, IMO.

I think that the optimal setup is a regular Colt spring, up to a Sprinco White or Hot White for Carbine buffers and Colt up to Tubbs SS for A5 or Rifle buffers. And tune gas to match, or buy a barrel that doesn’t suck. It seems that many barrels are ported to run steel case with an H3 and Sprinco Blue, because every dude on the internet is claiming that his setup is pure gold, so dudes are buying guns and throwing crazy shit in them. Its a snake eating its tail.

Sprinco springs rust. Fast. I get it, you want one because Mike Pannone likes them and they last forever. My Blue, Hot White, and White springs rusted significantly in about the lifespan of two Colt springs. So, they cost more and did not last longer. Yes, that rifle was abused somewhat. You guys in the desert can disregard, along with dudes that shoot in dry weather or at least dry and clean their guns immediately after use. Blue is too much, I’d choke down my gas if Blue runs well in adverse conditions. I liked the Hot White, a lot, because it goes into battery more vigorously, but that energy is coming out of the rearward half of the cycle.

Tubbs SS is too much in a Carbine sprung system. In an A5, the Tubbs is similar in strength bottomed out as a Colt spring, and a bit stronger in battery, as I’ve measured. So its not optimal as a solution, but it does work without adverse effects, in my A5 lower. I’m using a Tubbs SS on a dedicated suppressed rig, simply because it was a quick fix. I choked the gas down when I put the thing together, and it was still a little gassy. The spring works in this situation, but choking the gas back some more would 100% be the right answer. I’ve used other uppers, unsuppressed on this lower, and nothing crazy happened.