Carbine Buffer in a Suppressed 11.5" Upper?

[MistWolf]

My curiosity piqued by recent discussions about buffers & REs, I tested a carbine weight buffer in a suppressed 11.5" upper. The upper is from my Wolf Pup pistol. It has an 11.5" barrel from PSA, standard BCG, SLR adjustable gas block and an Omega suppressor directly threaded to the muzzle. The lower uses a pistol type carbine RE with H buffer and Colt action spring.

The gas block is adjusted so the Wolf Pup will lock back on the last shot and will do so even with heavy fouling. The action is kept lubed by applying a couple of drops of oil every few hundred rounds. Closing the SLR one click usually means the Wolf Pup will eject but not lock back. On the day of the test, the Wolf Pup was heavily fouled but freshly lubed. Temps were the high 20s. Closing the gas block one click with the H buffer resulted in the round firing but did not cycle the action. Opening it back up one click restored normal operation.

I installed the carbine buffer and performed a lock back check, that is, I loaded a single round in the mag. loaded the rifle and fired. As the buffer was lighter, I expected recoil to feel a little sharper from the buffer hitting the RE faster. The action seemed a little quicker, but not enough to feel any sharper. I closed the SLR one click and did another lock back check. To my surprise, the rifle didn't cycle at all. I repeated the same check with the H buffer and got the same results. Under these conditions, there was little difference between the carbine and H buffers. The action seemed to cycle just a little quicker with the carbine buffer, but that is just a guess on my part.

I also have a Colt 6933 lower with an A5 RE and A5A2 buffer. Running the Wolf Pup upper on the Colt lower, I need to open the SLR one click to get a lock back. The 6933 upper also wears an Omega suppressor and uses a BRT .063" micro port. Function on the Colt lower is just right. I didn't test the Colt upper on the Wolf Pup lower because it was late in the day and the temps were dropping with the setting sun. I didn't test the H2 buffer because I forgot to bring it along. Next time, I will.

In conclusion, the carbine buffer worked just fine with the gas flow adjusted to match. The gas block setting was the same for both the carbine buffer and the H buffer. I was unable to test with the H2 buffer. However, I believe tuning a suppressed 11.5" to run with a carbine buffer is less than ideal as there is evidence that tuning a suppressed upper to run with a heavier buffer reduces fouling in the chamber. I think Bufford T. posted something about it. I'm going to get some heavier buffers and test them.

[markm]

Run that CAR buffer with the block wide open. :p

We've only really felt more "pop" on the heavy buffers. Like you felt... the light stuff doesn't pop hard, it just doesn't run optimally. Choking a gun down to run the CAR reliably is, in my opinion, pushing the balance out of the sweet spot.

Interesting post though..

[MistWolf]

Run that CAR buffer with the block wide open. :p
No, thank you!

My first setup with the Wolf Pup was with a 10.5 Odin Works barrel that has an .083" gas port and non-adjustable gas block. At the time, all I had was a carbine buffer. The carrier hit the hammer so hard there was a sharp, painful sting to my finger through the trigger and that was unsuppressed! Switching from a carbine buffer to an H buffer took some of the sting out, but it wasn't nearly enough. Of course, it was frustrating at the time, but it set my feet on the path to greater knowledge. I have to thank CoryCop25 for hooking me up with my first SLR adjustable gas block. That let me test different combinations with varying gas flows and gain a few important insights.

[BufordTJustice]

I have found that increasing buffer mass, among other things, does help reduce fouling on fired brass and in the chamber.


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[markm]

My first setup with the Wolf Pup was with a 10.5 Odin Works barrel that has an .083" gas port and non-adjustable gas block

My first SBR was an 11.5" Sabre Defence with a port about that big. This was right when "we" were learning about H2 and H3 buffers. I just assumed that SBRs were miserable to shoot, and I put the thing in the safe and rarely shot it.

It gripes my ass that the industry is still full blown retarded at sizing ports.

[BufordTJustice]

My first SBR was an 11.5" Sabre Defence with a port about that big. This was right when "we" were learning about H2 and H3 buffers. I just assumed that SBRs were miserable to shoot, and I put the thing in the safe and rarely shot it.

It gripes my ass that the industry is still full blown retarded at sizing ports.

Yeah, those Sabre barrels were decently accurate, but had gas ports like the fuggin Mississippi.

Between my Sionics 11.5” RGP and my BRT Optimum 16”, I don’t have any better ported barrels. And, that being the case, they both STILL wear Ti SLR Sentry gas blocks because they both get suppressed.

On extended length gas systems, there really is no excuse.


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[M Sadler]

My first SBR was an 11.5" Sabre Defence with a port about that big. This was right when "we" were learning about H2 and H3 buffers. I just assumed that SBRs were miserable to shoot, and I put the thing in the safe and rarely shot it.

It gripes my ass that the industry is still full blown retarded at sizing ports.

It's a conspiracy orchestrated by the adjustable gas block manufacturers. Seriously though, as long as the unwashed masses keep buying them, manufacturers and retailers will find a way to get them to market.

[MistWolf]

I have found that increasing buffer mass, among other things, does help reduce fouling on fired brass and in the chamber.

I came across your posts on the subject and read them with interest. It got me to thinking, so this weekend, I drove out to the desert with my two shorties and different buffers. Testing with the SLR equipped suppressed 11.5" upper showed that the Carbine, H and H2 buffer all ran on the same setting. However, recoil was a tick sharper and felt quicker with the Carbine buffer. Of the three, the H2 felt the softest and slowest.

Next, the SLR upper was tried on the lower with the A5H2 buffer and green spring, it felt even softer than the H2 and almost too slow, until shots were fired rapidly. The combination with the flattest recoil was the SLR upper and A5H2. Next flattest was the same upper with the H2.

The SLR upper was tuned using the lock back check. It was tuned until the round would eject, but not lock back. Opening the gas port one more click resulted in full ejection and lock back. On this day, the SLR gave full function on the same setting with all four buffer types.

The second upper tested is a suppressed 11.5" Colt 6933. It comes from the factory with a gas port that measures about .073". Unsuppressed, it worked fine but felt a little over gassed. With the addition of a suppressor, recoil became uncomfortably sharp. I bought a BRT Micro Port kit. Based on the specs of the AR (11.5" barrel, carbine gas system, A5H2 buffer, shot suppressed only) BRT sent the kit with a .063" micro port. Recoil isn't as soft as the SLR upper but I have no doubt the Micro Ported Colt upper will work even when cold and heavily fouled. When the SLR upper was tried with the H2 buffer, recoil was noticeably sharper.

I didn't collect the brass to see if there was a noticeable reduction in fouling. The grass where I stopped to shoot was 3 - 4 inches thick and made finding the empties challenging.

That the SLR upper fully functioned with all four buffer weights leads me to believe that while the proper buffer weight is important, having the right gas drive is more so.

[BufordTJustice]

I came across your posts on the subject and read them with interest. It go me to thinking, so this weekend, I drove out to the desert with my two shorties and different buffers. Testing with the SLR equipped suppressed 11.5" upper showed that the Carbine, H and H2 buffer all ran on the same setting. However, recoil was a tick sharper and felt quicker with the Carbine buffer. The H2 buffer felt softer and a little bit softer. When the SLR upper was tried on the lower with the A5H2 buffer and green spring, it felt even softer and almost too slow until shots were fired rapidly. The combination with the flattest recoil was the SLR upper and A5H2. Next flattest was the same upper with the H2.

The SLR upper was tuned using the lock back check. It was tuned until the round would eject, but not lock back. Opening the gas port one more click resulted in full ejection and lock back. On this day, the SLR gave full function on the same setting with all four buffer weights.

The second upper is a suppressed 11.5" Colt 6933. It comes from the factory with a gas port that measures about .073". Unsuppressed, it works fine and compared to the SLR upper, felt a little over gassed. The addition of a suppressor turned the recoil uncomfortably sharp. I bought a BRT Micro Port kit, informing BRT of barrel length, buffer type will always be shot suppressed. Used with the A5 lower, recoil is much improved. Recoil isn't as soft as the SLR upper but I have no doubt the Micro Ported Colt upper will work even when cold and heavily fouled. When tried with the H2 buffer, recoil was noticeably sharper. This upper needs the heavier A5H2.

I didn't collect the brass to see if there was a noticeable reduction in fouling. The grass where I stopped to shoot was 3 - 4 inches thick and made finding the empties challenging.

That the SLR upper fully functioned with all four buffer weights leads me to believe that while the proper buffer weight is important, having the right gas drive is more so.

EXCELLENT post, Mist.

I suppose that, to clarify, I consider the Vltor A5H2 and the std H2 carbine a "heavy" buffer.

I suspect that the LMT enhanced carrier also plays a meaningful part in the cleaner brass.

It's also possible that the SLR block offers a more finely granulated adjustment reference to the lower limit of function, as you hinted at.

I dare say, as you have observed, that regulating gas volume at the gas block is a virtual given at this point, when it comes to suppression.


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