Mid-Length vs Carbine Length Gas System

[InTheSwamp]

Mid 16" with fixed GB and a Slash Heavy Buffer (6.5 Oz). Runs smooth.

 

[ECVMatt]

@ECVMatt - what is the buffer weight you’re using in any of your carbine stocked rifles?

Most civilian AR’s with carbine buffer systems will have grossly underweighted Carbine buffers at only 2.9oz, whereas a Rifle buffer is 5.2oz. Kick in an H3 or Vltor A5H2 buffer at 5.3-5.4oz, and the difference in recoil impulse for the same upper on a carbine vs. rifle lower almost completely evaporates. The bigger trouble happens when folks have a grossly oversized port (intentional by barrel makers to ensure function) but then run a lightweight carbine buffer - these run, obviously, but they beat the hell out of themselves, just to avoid immediate customer service calls.

That is a good question @Varminterror. They are both LE6920's and I have not checked. I reread your posts and they make a lot of sense. Both of my carbines eject to the 3 o'clock position and don't chew up my brass, but the perceived recoil is greater than my mid-length/rifle/muzzle break rifles. I think the sum of parts has a lot to do with this as well.

I have not played with buffer weights, but will give it a try!

 

[Varminterror]

@ECVMatt - a 6920 SHOULD have an H2, but I can’t say if Colt has held true to design throughout all eras of production.

 

[DMW1116]

If a barrel has a large gas port and an AGB is added, does that mean the AGB becomes a wear point?

 

[Hugger-4641]

If a barrel has a large gas port and an AGB is added, does that mean the AGB becomes a wear point?

No, it won't wear per say, but it does become another part that if not installed properly, can loosen up and need screws tightened. Will also need cleaning at rare intervals.

 

[Varminterror]

If a barrel has a large gas port and an AGB is added, does that mean the AGB becomes a wear point?

No, not really. The orifice of the gas block still does the majority of the restriction, so the trailing edge of the port inside the bore remains the major wear point, and the gas block set screw really doesn’t take wear. Gas block set screws tend to foul, not erode - so it’s a good idea to cycle the screw from time to time if you think you’ll want it to remain adjustable over a LOT of rounds.

I generally replace gas blocks when I replace high round count barrels, but I’ve taken a few gas blocks across multiple barrels - so when I’m 80-100k rounds on the gas block, eh, I’m not bothered by replacement.

Technically, gas tubes are wear items. Very, very few people ever end up replacing a gas tube in their life. I don’t ever remember replacing any of mine as PM, only rather I replace the tube when I replace the blocks, and replace the blocks during one of the barrel replacements.