Great advice, thanks. It functioned fine for a couple years, after the gas piston conversion was gunsmith installed. Didn’t fire it for the last 10-15 years, just set clean and oiled in my safe. Took it out to check the zero on the iron sights, (was still on about 2” low from POA at 25 yards). Just started short stroking, fte, ftf. Took the block off, cleaned it thoroughly, and the barrel gas port. Noticed the hole inside the block was chamfered (like a deep deburr) deeply, twice the diameter of the hole, at least. Gave me a good feeling about the blocks’ clock position, if just a tad off, would still flush all the expanding gas needed to work the action. There is no adjustable gas setting on this $400. Conversion kit, that I can see. No index marks or “S” or “N” indicators stamped anywhere. Those are clearly stamped on my LWRC M6A3 carbine. Just checked my LWRC, it’s marked N, S, A, C. Need to read my manual on that, no clue what the A or C stands for. I’ve never messed with adjusting AR gas ports. Buying a can for a center fire caliber rifle/carbine seems to be a futile, expensive, troublesome endeavor to me. Good idea about switching this carbine back to DI action. Going to take it out to the range one more time to test function. Also I found the cap screws not torqued down tight again, today after consulting a gunsmith about tweaking the block position. When I had the block off, I noticed a deep cut across the barrel, and four deep drill starts that seemed be matched to the cap screw shank ends. So the gas block screws will unavoidably slide into that exact position as I torque the screws down? WTH? That’s how it’s done?This is a dead horse in the AR world but it's always fun to read and respond
Did it run before you put the kit on? Any Issues?
If it's short stroking and FTE, why would you consider a heavier buffer? No need for that mess. Focus on the issue at hand, which is the thing you put on the barrel of the perfectly good gun that is not working at the moment.
Also, those kits from CMMG are supposed to have an adjustment on them for regular and suppressed. If it's in the the lowest (more closed) position, it can malfunction...you're supposed to be able to almost close the port.
The two options I would entertain:
1. Remove the kit and return it to it's former self that you know works. Either sell the kit to some sucker on here or chunk it. Be happy with gun. I'm serious, not a joke.
2. If set on keeping it, you have to deal with its problems and know there's a good chance it's a terminally unreliable gun.
Reminder Per @mr ed use the shim/spacer that came with it or and least get it spaced off the shoulder correctly on the seat.
DISCLAIMER: I don't have any piston kits on any guns anymore. Not worth the hassle. All are direct impingement. Only piston uppers worth a crap IMO are purpose built from the company.
With that DISCLAIMER, these are things I have done to get a piston conversion set up correctly.
On the barrel, Mark centerline (of barrel-TDC) front and rear of the gas seat with a sharpie or something else you can see that doesn't jack your barrel.
On the barrel measure distance from shoulder to rear of port - write it down.
On the gas block, measure distance from rear of block to rear of port - write it down
do the math for the space you will need to offset the shoulder.
Measure both the barrel port and the gas block port (mostly so you know how much slop you do or don't have. They should be sitting right about .070 for a 16" carbine gas. Older guns, the barrel port may be as low as .062 or something. Whatever it is, the gas block should be at least the size of your barrel port. They are almost always way oversized for slop and for whatever their little adjustment system is.
Seat your GB per your measurements above. Torque your setscrews and use BLUE threadlocker. You can use green but life will be difficult if you need to remove it.
DON"T USE RED THREADLOCKER. You will need a torch to get it off and it usually requires drill bits and easyouts. Bad move.
Finish setup per the instructions.
When you shoot, make sure you are on the most OPEN setting. As you shoot a round at a time, dial it down until you have a malfunction. then back a couple clicks.
If there are only two settings, put it on the highest.
If there are only three or four settings, put it on the one closest to the middle, and turn it up if it starts to malfunction.
NOTE: If your gun ran fine before you slapped that Frankenstein neckbolt on it, there is absolutely no reason to spend time or money on anything else like buffers, trigger springs, bolt knickknacks, or whatever widgetry someone thinks will solve your problem. Your problem is the gas system you manipulated so that should be your focus.
If you have to drill out your gas port larger than what's on this list or what ran great for 20 years, you might be a redneck. Recommend you don't.
Now, I do see a lot of barrels with a carbine gas and a .075ish port...they do that so there's no doubt it'll run...not very good AR smithing but effective - P for Plenty I guess.
AR-15 Gas Port Sizes
Information to help you decide which gas port size may be suitable for your buildtacticalmachining.com
