AR-15 Gas and Recoil Tuning

[Saltyag2010]

This.
Spent brass can tell you a lot.

Brass looked undamaged and normal except for the rounds that tried
to double feed. Those had a gouge from the bolt lugs near the neck on the case.

Its not dirty yet. I can check out the gas block.

 

[AaronP220]

Some of y'all have too much of a hang-up on gassing, IMO. Define "over-gassed" for me. If a gun will run with less pressure, does that mean it is truly over-gassed? If that's your only definition, then that's just ridiculous. Go ahead, fine tune your "Ferrari" (probably a fricking polished turd Oly Arms with an adjustable GB) to the absolute minimum pressure, then subject your weapon to a little dust and dirt and then tell me how it ran.

Hey old friend!

I define over-gased as anything over the reasonably lowest setting required to operate the rifle 100% of the time, in any condition. Most ARs from the factory are over-gassed. It means that the gun will run 100% of the time with any ammo you chunk in it and it's a safe way to go. What that does though is increase bolt speeds and wear, gas ring wear, and introduce more heat and fowling into the action. Gives people reasons to sell H2/H3 buffers, heavy springs, "Improved reliability" bolts with an extractor that's got millions of lbs of tension on it. When the gas system is tuned correctly you can run a carbine buffer and std light ass spring, you don't need fancy extractor devices and all that. There's more to it than just turning the gas down so it will run on the absolute minimum. Timing is a big issues as well.

I found out first hand what running extremely over-gassed does. In my Green Mega, which pretty much runs suppressed %100 of the time - literally shattered the gas rings (all 3 of them) into chunks of hard steel in under 1,000 rounds. I cracked two lugs on the Young Man. bolt. That's what sent me down this road of tuning gas systems. On my CMT build, which also ran suppressed most of the time, I destroyed the gas rings in about 600 rounds. The bolt was fine but was showing significant wear - wear that I would expect to see after 5-6,000 rounds. So I've swapped to adjustable blocks. I turn it down to the point where the bolt will lock back 100% of the time (which is what's usually called the minimum gas setting) and then add 1 or 2 clicks for added insurance.

If you like, come grab one of my rifles and live with it for a while. Shoot it, get it dirty, see if you can get it to stop. I put about 1,100 rounds down my 10.5" SBR with a tuned gas system in about 10 hours and didn't have a single issue other than two PMAGS shitting the bed on me.

 

[40Arpent]

Hey old friend!

LOL!

 

[popper]

Saltyag - don't know if you really got a good answer. Consider that it takes a defined psi at the gas key to unlock the bolt. Also consider that the lugs bolt/extension have friction that holds the bolt closed. What you want is enough key psi to unlock when the chamber psi is low enough to reduce wear on the lugs/bolt pin/gas rings/etc. The extractor claw has to pull the case out of the chamber so if the chamber psi is high, brass has not sprung back enough and frictional hold in the chamber is high so extractor can wear. BCG/buffer mass is there to control the spring rate, like shocks on a wheel. If the spring is not 'damped', bolt can bounce on the case head and give problems. This is to control fire rate in full auto. It is a mechanical system so the better 'tuned' the better it performs.