Hey guys,
First time posting on the forum. I usually just read and get ideas etc. I’m wanting to do my next build in 7.62x39. I’ve read about guys having issues with the caliber in the AR platform. I’ve seen guys talking about enhanced firing pins, certain mags are better than others, use a heavy hammer spring etc. Can anyone share their experience with the 7.62x39 ARs? Tips, things not to do, things to avoid etc. Thanks in advance!
Welcome! I don’t have a whole lot of experience with this platform, but will soon. I’m sure somebody more helpful will come along tonight or tomorrow. It’s my understanding that usually running C-Products or ASC magazines will help a lot. Enhanced firing pins are necessary to reliably run Russian ammo with those hard primers. Most if not all half decent manufacturers realize this now and a complete upper will come with one assembled. If this isn’t the case, it’s a cheap and easy fix. You shouldn’t need a heavy spring with the enhanced firing pin. Standard buffer setup should be fine too. As with any other build (actually more than most of them) YMMV.
My first AR was in x39. It was a bit of a Frankenstein but mostly PSA with a Tactical Ambush BCG. it was built several years ago and I got it through an estate sale. The only real problem I had with it was the M4 feed ramps were designed for a .223 so I had to open them up to .312 but I think most rifle manufacturers have learned that lesson. I’ve heard that some mags are better than others but I’ve heard that about every caliber out there. Just buy good mags and test each one. Other than that I have no problems with my commie AR. Runs like a top. A very mean, bad ass top 
This caliber on a standard AR-15 lower can be trouble. One of the big problems is that the magazine has to be straight for a couple of inches to fit into the magwell. Thats part of the reason we have the KS-47. It is designed to use standard AK-47 style magazines to help with the feeding issues, while still keeping the normal feel and controls of the AR platform (minus the mag release). They can be difficult to get your hands on because they normally sell out very quickly, but here is the link to them on the website.
I built one of these earlier this year. Used a PSA lower receiver and PSA lower build kit. upper is a Bear Creek Arsenal complete 16" upper. mags are Midway USA AR Stoner 10 round metal.
runs brass ammo decent. did have a few failure to feed issues when everything was new.
now with the steel ammo it ate the wolf ammo with no issues, it does not like the tul ammo, would not fire and had light primer strikes on every round. found out Bear Creek now has an enhanced firing pin that is standard in all of the 7.62 uppers. according to the reviews online this solved everyone’s issue with light primer strikes. order one and put it in.
have not been able to test out yet as I am not allowed to use steel at the range I usually go to.
Forgot I had picture from range that I tested at.
The only Hardened Arms upper that I had problems with, was their 7.62x39 upper.
It had trouble ejecting. The 7.62x39 is about .440 diameter at the base, vs. about .378 for 5.56x45.
But the ejection port on the HA 7.62x39 upper was only a 1/2 inch across - same as 5.56x45 !
And so … it had troubles cycling !
I think the 7.62x39 is one of THE BEST single calibers.
BUT it is poorly implemented … sort of. Want more muzzle velocity ? Get a 7.62x39 with a 24 inch barrel. Which will be very expensive. The longest barrel I’ve seen off the shelf is 20 inches for a 7-39.
Also the VARIETY of 308 is super helpful. Imagine if Barnes made a 165 grain 7-39 diameter bullet (303, 311, whatever it is). I can fit 33 grains of 2200 (a faster burning rifle powder) in a 6.8 SPC and it works really good. The 7-39 has a little more case capacity, and is a little more tolerant of fast-burning powders, than 6.8 SPC.
34 grains of 1680 pushing a 165 grain ? well that’s very similar to 35 grains of 4198 pushing a 165 grain Barnes.
Since I broke a 6.5 Grendel upper using only 1.7 grams of 1680, I have a lot of respect for it !
I think the best way to get 7.62x39 functionality is to buy a 308, and to simply load it with 7.62x39 size loads … sort of.
I use 35 or 35.5 grains of IMR 4198 or Reloder 7 in 308 loads.
You can fit almost that same amount of powder in a 7.62x39. AND, you can use a faster burning powder … which generates more pressure for its weight = more foot-pounds.
ALSO … the 7-39 rifle is FANTASTIC reliability wise. I have only seen it in pictures, but there’s so many people praising the historic 7-39 … it does make me curious.
How do the classic 7-39 rifles achieve their reliability ?
I’ve put over 1k rounds thru my 7.62 AR and never had a single issue. Its a Radical Firearms upper on an Anderson lower.
Did you use a complete Radical upper?
Yes
use an h2 buffer, enhanced buffer spring, enhanced polished trigger, an enhanced firing pin in the 7.62x39 BCG, and use ar stoner magazines they bought acs, and it will effortlessly mag dump russian steel casing. i use a bear creak upper however typically the same thing can be done to any ar47, also ks47 as well im assuming using their listed magazines.
I had heard of the various issues some were having with 7.62x39 in their AR Builds. That being said, IMO it was a no brainer buying the hybrid KS47 upper and lowers from PSA. Both my 8" pistol and 16" rifle have been issue free after thousands of rounds. More rounds through the 8 inch, It’s my favorite!
Is your x39 a pistol or carbine? I heard of using an H2 buffer in pistols but not so much in a carbine.
two things, not to be rude because then i get deleted… but i don’t believe anyone who says they haven’t had any issues even doing the things i mentioned. ■■■■ happens if you want a real zero issues carbine stick to 556 thats always going to be my go to. that being said, i have had the most unbelievable great results with this specific build, it is a pistol length system for 7.62x39 i dont plan on distance shots you get the most out the ammo within 100yards. can mag dump regular steel russian hp ammo, and it really really loves bimetal casing it runs like brass can mag dump, bolt locks back swap and mag dump. now lacquered casing is horrible in carbines no matter the caliber that stuff will give your no issues 556 its first issue… i highly recommend staying away from lacquered.
it absolutely needs the h2 buffer no matter the length, some people even use h3. my preference is for the h2 because the bolt locks back everytime. i also highly recommended the enhanced spring while you’re at it it stays cleaner and is about 15% to 20% stronger. its the driving force of the extra weight that is slamming those rounds in and forcing it to cycle
now, eventually this can potentially break your extractor, so get a few spare ones as well.
We used a fail zero nickel boron bcg, h2 buffer, C mags, and polyperformace ammo, no problems ever. Some guns with some magazines will not feed properly. Sometimes the ribs on some magazines hang-up the 762x39 and will not allow the bcg to push the next round out of the magazine.
Have probably 1.5k rounds through my x39 carbine. Have had a lot of fail to feeds with it. Tried several different mags, the 20 round CPDs have been the most reliable for my gun and solved the fail to feed problem. Gas tuning may have helped, unsure though. Barrel has the wide “300 blk” ramps, according to the manufacturer.
Everyone will claim this works and that doesn’t. Like that poster a few posts up saying stay away from lacquered case ammo. That’s not a problem at all for my gun. That’s the kind of advice need to watch out for. You’ll need to troubleshoot your particular gun because they won’t all be the same.
But there is one thing that needs to be addressed with every build that you intend to feed Russian steel cased ammo, and that is the firing pin.
An enhanced (longer) firing pin is a must. And they’re cheap. BRA make a great enhanced pin. You MIGHT be able to get away with a mil spec AR pin, but why bother.
And the real reason you should get a longer tipped pin is because Russian mil spec 7.62x39 has a slightly recessed primer compared to 5.56. Take one of each cartridge and run your finger tip over the primer, you’ll see what I mean. The 5.56 primer is pretty much flush with the case. A regular mil spec pin jus won’t be able to strike deeply enough to set off the primer reliability.
Maybe the Ruskie primers are harder or maybe they aren’t. It doesn’t matter if you get the longer pin. Currently I’m using a LaRue MBT-2S trigger with the 2.5lb spring that comes with it and I haven’t had a single fail to fire in a long, long time using the BRA pin. Maybe 1k rounds. It’s all about the pin.
Some people claim a heavier hammer spring is needed. That was zero help for my gun. Now I’m using super light springs in the FCG with a longer pin and it sets off Russian steel ammo with near 100% reliability.
Your results may vary.
I have a basic carbine buffer in my carbine x39. Only problems I’ve had was with some very old copper washed chinese ammo that I wanted to burn through to get rid of. That stuff refused to extract every time. After a few rounds I tossed the rest back in the bag to get taken apart later, which I did. I never had any issues with Russian lacquered steel. I’m shooting brass now and have zero issues. I don’t know how many rounds I have through this rifle, all I can say is lots. I haven’t broken my extractor yet so maybe not enough. In fact, I’m sure I haven’t shot it enough so I’ll take it to the range and put a few more boxes through it just for fun.
I have 2 in 7.62x39 My first is a KS 47 and it works well. I have been an AR guy forever so struggle a bit with the mag insert and no bolt hold open. That is on me, and not the gun. I then bought an Anderson upper and paired it with a Palmetto lower that I had. It was under gassed and required a very slight opening of the gas port in the barrel. Once that was done it has worked fine. with Wolf and Tula. I have not been willing to shoot them a ton just because of the world that we live in today, I don’t want to burn what I can’t replace. They each have about 150 rounds in them to function test and zero them.
