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 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.
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