Question; is there a buffer low weight minimum, not to pass or go below?
What options are there if positive cycle rate performance incurs carrier bounce?

I’m currently at 2.6oz buffer (using Strikes’ Optima Buffer kit for weight mgnt.) My brass ejecta have gone from 5 – 530 up to about 330 o’clock and from not cycling new rounds to consistent feeding, with Brass, Steel (Tula 55g) is still not auto feeding.

I’m looking for help with cycle rates Using a Adams Arms rifle length kit on a 20” Faxon, it is so far been performing under gassed.  I read through the STICKYs here re short stroking and Buffers…all great reads and confirming science/known engineering. Rather than go straight to opening the port, Im playing with the other end of tuning.

The port on the 20" Faxon, 556 I have is 0.078. I confirmed with Adams Arms responded that their rifle kit should operate with a 0.098 port. So I know Im under-gassed. Machining and drilling holes is pretty straight fwd but not reversible. I might want to use the barrel for a DI rig eventually if this piston party flops.

Considering the timing to pressure on the bcg is a lot different on pistons, I will re-evaluate going lighter rather than heavier. I started with a standard, 32 coil springs and 3.06oz buffer and full open adjustable block. The performance progress trajectory I’ve gained going to a lighter buffer spring and weight show positive feed back.

I will also look into the bolt lock test, but I’d have to switch lowers. This rig is a Commiefornia special running a Juggernaut Tactical kit….these replace standard bolt catch for a mag lock and release.

i've had to enlarge the gas port on a few builds when switching from DI to piston, especially when doing 7.62x39.  You can always use an adjustable GB if you want to go back to DI.  or those restricted gas tubes.  I'm under the impression that carrier bounce can be mitigated by using the normal USGI buffer with the loose weights inside.  that's why it rattles, sorta like a dead-blow hammer filled with shot.

don't know nothing about no aftermarket fancy gizmo buffer systems, I don't use them.

a similar data point for you:  my 20" Criterion 5.56 barrel comes with a 0.089" gas port, rifle-gas length, set up for DI.

I do have another 20" 5.56 rifle-gas set up for AA piston, but I didn't measure the gas port on that one when I built it.

before I drill the gas port, i do some math on the gas-port cross-sectional area, using pi-r-squared, and my wire-gauge, alphabet, and fractional drill bits.  Depending on how undergassed i am, will then estimate a desired target percentage gas-port increase.  5-10% will make the difference between a std 3oz buffer, and a H3, sometimes, depending.  So you really need to sneak up on it.  Might be an iterative process, has been for me, usually.  Disassemble, calculate, drill, clean-up, reassemble, shoot.  Repeat.  Tedious.  Aiming for that perfect setup that just gets you to last-round-bolt-hold-open, consistently, repeatedly.

Thanks rpoL98
"5-10% will make the difference between a std 3oz buffer, and a H3, "

I'll take math estimates over trial and error. Thanks for that suggestion. essentially the same process with the buffer weight. "sneaking up to it". Playing with the buffer was also an interim attempt for a solution before I could get a proper set of machinists bits. The fractional gaps with bits at home depot are not satisfactory.

here's another equation i been pondering;
for the balance of (gas port) x (gas length) x (friction Q) x (BCG weight) x (buffer weight) x (spring Q) = n  ??



https://live.staticflickr.com/65535/53738858296_ae2437599d_w.jpgMachinist Drill Bit Size Table