ar15 in 7.62x39

[a1rfreshener]

so i currently have a rifle set up in x39 and i seek proper function with last shot hold open. so im thinking the rifle is under gassed and that the bolt isn't going back far enough to lock up on the last shot, so to remedy this i am thinking of going to with lighter bolt carrier that is not full mass. im going this route because im almost certain that its currently running a carbine buffer and to my understanding that is the lightest buffer available. I also shoot the cheap tula which is usually under charged i feel.

so my options:
-go ghetto and trim a half inch off the polymer at the end of the buffer to save weight.

- combination of above with coils clipped off of the the buffer spring 1 at a time of course.

-more expensive route would be to buy a lower mass bolt. that brings up a question. will any standard ar15 5.56 bolt carrier work? or is there something different on the inside that i cant see. that would force me to purchase a x39 bcg.

[CMBrowning]

Before you spin your wheels, make sure your gas block is spot on. What mags add you using? I run asc, c products or ar stoner. Standard buffer and buffer spring.
I shoot tul ammo about 80 percent of the time. No issues, no short stroking or bolt hang up.

My arak21 in 7.62 has ran flawless
My PSA carbine and pistol both run flawless. They are also in 7.62.

[kenl]

^ +1. Also, where are your empties landing? IIRC, 12 to 3 o'clock, over gassed, 3 to 4:30, just about right, 4:30 to 6, under gassed.

I run a m16 bolt carrier with a standard buffer spring and a carbine buffer with no issues. The rifle loves Tula hp.

[ratled]

+2

Kenl would never double cross you................

ratled

[bh796b]

Hello I'd like to chime in with a question I don't mean to hijack the thread. But kenl brings up a comment that makes me wonder about my personal set up. My casings shoot out in the 12-3 position which you stated is caused from over gassed. Is that anything that will harm my AR in the long run. Any problem with being over gassed? I'm new to the forum, guns and especially AR builds and was just curious. Thank you!

[C.W.M.V.]

I think the right answer has already been covered, make sure the gas block is aligned correctly.
Good ammo would help too.
For my pistols I just opened up the gas port and put on an adjustable gas block. Now they run any ammo all the time.

[Jimi Jah]

You should have plenty of gas to keep the BCG open, if not it's not aligned or the port is too small. I used a JP adjustible gas block on mine, tuned it so the bolt stays open but the recoil is reduced.

Have the gas port checked as well. I've had barrels with a burr left inside that causes all sorts of problems.

[rosenbaumtravis]

My experience with 7.62X39 was pretty straight forward. My guns will run on the standard carbine buffer and BCG just fine. I did have slight cycling issues with light ammo on my 16" mid length upper. Did all all required checks and then opened the gas port slightly. Solved my problem.

My 16" carbine length upper has cycled 100% with pointed bullets. Round nose bullets sometimes hang on the feed ramps. I use 10 round CP/ASC mags.

I would verify that your gas block is aligned first. How does the fired case look? Are there any unusual marks that would point to a burr or rough chamber? Check all points of failure such as carrier key, gas rings, gas block, and verify you are not using an incorrect length buffer or spring before opening your gas port. Another place to double check is the actual bolt release. Does it function smoothly or is it tight and or rough. I have had one lower that the bolt release would hang up and just needed a little lapping. I would recommend looking into the gas port as a last resort.

Just an FYI: you might want to keep a few extra extractors handy when shooting this caliber out of an ar. Ask me how i know....

[a1rfreshener]

thanks for the info guys. just took the hand gard off and the gas block seems to look ok. the port is clear as well. but i think i am undergassed remembering where my cases land. cause i will have a pile around my 5 o clock. i am also running a law tactical folding stock adapter. so there is also added mass to the bcg. if i were to open up the port how much do you think i should go up to?

[kenl]

thanks for the info guys. just took the hand gard off and the gas block seems to look ok. the port is clear as well. but i think i am undergassed remembering where my cases land. cause i will have a pile around my 5 o clock. i am also running a law tactical folding stock adapter. so there is also added mass to the bcg. if i were to open up the port how much do you think i should go up to?

I'd try a lighter recoil spring first. You would probably do fine drilling out the port, but you can get burs in the barrel, or have other issues. Sorry, don't know the usual size of the port, but I bet someone else does. Have you tried removing the folding stock adapter, to see if the rifle works without it? Like you said, it could be adding to your problem. Also check the bolt's gas rings. Make sure the gaps aren't lined up. Check the BCG gas key while your at it. You'll get an undergas condition if it's loose and leaking.

If all of that doesn't work, yeah, you might have a small gas port, and will need to drill it.

Good luck

[rosenbaumtravis]

thanks for the info guys. just took the hand gard off and the gas block seems to look ok. the port is clear as well. but i think i am undergassed remembering where my cases land. cause i will have a pile around my 5 o clock. i am also running a law tactical folding stock adapter. so there is also added mass to the bcg. if i were to open up the port how much do you think i should go up to?

What length barrel and gas system? I opened my 16" mid length to ~0.085. The required gas port size will vary with barrel lenght and gas system length.

I would recommend checking all other items above before drilling your port. Try it without the stock adapter as mentioned above. Does the bolt hold open when cycled manually on an empty mag?

If you decide to drill your port start small and work up until it functions. Also, make sure you dont drill into the rifling in the barrel.

When you checked your gas block, did you remove it to see if the port is top dead center with the barrel? Or did you just eyeball it to see if it is inline with the upper? I have seen ports drilled out of top dead center. I would pull the gas block and look for the circle of carbon build up around the port. You should have a fairly even circle of carbon around the port if it aligned properly. Its a very easy check and will eliminate the possibilty of a gas port that is off center.

[ar15barrels]

so i currently have a rifle set up in x39 and i seek proper function with last shot hold open. so im thinking the rifle is under gassed and that the bolt isn't going back far enough to lock up on the last shot, so to remedy this i am thinking of going to with lighter bolt carrier that is not full mass. im going this route because im almost certain that its currently running a carbine buffer and to my understanding that is the lightest buffer available. I also shoot the cheap tula which is usually under charged i feel.

so my options:
-go ghetto and trim a half inch off the polymer at the end of the buffer to save weight.

- combination of above with coils clipped off of the the buffer spring 1 at a time of course.

-more expensive route would be to buy a lower mass bolt. that brings up a question. will any standard ar15 5.56 bolt carrier work? or is there something different on the inside that i cant see. that would force me to purchase a x39 bcg.

You can remove one steel weight from the carbine buffer and replace it with a plastic spacer.

[a1rfreshener]

yea ill give it a shot, everything looks good on the gas block. i think im going to order a lighter recoil spring and and take apart the buffer.ill try to get to the range this saturday.

[Jimi Jah]

I used a powdered tungsten buffer in mine. You can adjust the weight with a powder scale. It avoids the clacking and cycles much smoother. With an adjustable gas block it's a smooth operator.

[CMBrowning]

How did things go? Have you verified the gas rings on your bolt are not aligned?