Originally Posted by
MistWolf
...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.
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