View Full Version : Adjustable gas block tuning, changing buffers?
I am going to experiment with an adjustable gas block on a pencil barrel build. My goal is the softest recoil and least muzzle movement while remaining reliable with the one load it is tuned for.
A common recommendation is to close down the block until the bolt just locks back on an empty magazine then open it some amount e.g. half a turn. That doesn't seem precise. Would a better way be to tune it to just lock back with an H or H2, then leave it there and run a standard carbine buffer?
Without intending snark (because I know it may “sound” that way), how is that actually more precise?
My instinct would be to tune with the intended buffer, just to limit a variable. Others that know their stuff seem to typically use the H2 or A5H2 buffer as the baseline, though I don’t see how there could be any problem using an H.
ColtSeavers
07-30-20, 10:15
Why would you test for one variable (H2 buffer), and then change it for another one (swap in standard Carbine)?
The point of an adjustable gas block is to not have to change buffer and recoil spring weights.
Use both a standard weight carbine buffer and recoil spring, adjust off of that for reliable bolt lockback. The reason you then open up the port another half turn or whatever is to account for variables such as weak ammo and colder temperatures, as examples.
No snark inferred. I can easily weigh the buffers to quantify a difference. I cannot measure how much more gas passes with half a turn.
No, changing buffer weight affects several things at once.
Adjusting the gas block only affects gas drive.
A better way to assess reliability margin is to shoot with a loose hold or pistol grip only hold and check for lock back.
A common recommendation is to close down the block until the bolt just locks back on an empty magazine then open it some amount e.g. half a turn. That doesn't seem precise.
Would a better way be to tune it to just lock back with an H or H2, then leave it there and run a standard carbine buffer?
The reason you then open up the port another half turn or whatever is to account for variables such as weak ammo and colder temperatures as examples.
Yes, I understand that. I thought making sure it would lock back with a buffer one or two steps heavier would also account for these variables. But I am happy to be corrected, and I'll tune with the parts I intend to actually run. Thank you.
Do you already have the barrel, etc?
If light weight and low recoil are the objective, the BCM 14.5 ELW middy with their perm gunfighter muzzle device is the answer. It is BOTH my fastest shooting/shootable and lightest AR at the same time (H buffer)
Adjustable gas blocks do not offer fine tuning. There's really only one setting that both reduces gas and still cycles... one click down and the gun won't run good, and number of clicks open, and there's no gas reduction.
I already have this built around a Faxon 16" pencil barrel. The gas block is from Wojtek Weaponry and one of the only 0.625" adjustables I could find in stock at the time. It's a simple screw style block so infinitesimally adjustable in theory.
It's a simple screw style block so infinitesimally adjustable in theory.
Mechanically, Yes. Gas functionality, the open most settings do nothing. You'll see what I mean when you use it. When you get to an adjustment that actually starts to restrict some gas, there'll only be a click or two before the gun won't cycle well.
What do you mean by click? There is no detent on the adjustment screw, only a separate grub screw to hold it in position.
...Ahh, the simplicity and precision of fixed port sizes...
Mechanically, Yes. Gas functionality, the open most settings do nothing. You'll see what I mean when you use it. When you get to an adjustment that actually starts to restrict some gas, there'll only be a click or two before the gun won't cycle well.
What do you mean by click? There is no detent on the adjustment screw, only a separate grub screw to hold it in position.
Clint, there is a pretty good chance I'll be replacing this block with one of yours eventually but I either hadn't found them or they were out of stock when I was scrounging for parts earlier this month. In the mean time I hope to learn something about gas levels from the use of an adjustable block.
What do you mean by click? There is no detent on the adjustment screw, only a separate grub screw to hold it in position.
SLR AGB have detent clicks.
judgecrater
08-04-20, 17:07
I already have this built around a Faxon 16" pencil barrel. The gas block is from Wojtek Weaponry and one of the only 0.625" adjustables I could find in stock at the time. It's a simple screw style block so infinitesimally adjustable in theory.
The Faxon 16" pencil is an outstanding barrel. Incidentally, I have an adjustable gas block on that gun.
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