AR-15 build with 7.62x39

Discussion in 'AR-15 Discussion' started by GregTheHun, Jan 28, 2012.

  1. GregTheHun

    GregTheHun New Member

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    Hey guys, I was curious if anyone knew some things I wanted to ask about this AR build. I'm going to number them so you can refer to them easier and type less.


    1. Will a standard lower for a 5.56 AR accept mag that hold 7.62x39 (not AK mags, AR mags in 7.62x39, that I know exist)?

    2. Is there a way that I can build one with a gas piston system in 7.62x39?

    3. If I built a 7.62x39 gas piston AR, is there anything else I should consider when building one?


    Now, I know that some of you may consider this a terrible idea, and I understand your considerations. I find the 7.62x39 superior for what I would want it for, and it doesn't matter to me otherwise.

    I like the AR platform, but I want that round with a reliable gas system.

    Any other helpful websites with good parts and links to sites would help me greatly as well.

    Thanks all! ^_^
     
  2. Gatoragn

    Gatoragn Active Member

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    1. Yes a milspec AR15 lower will accept AR15 magazines made for the 7.62x39

    2. If the diameter of barrel at the gas port (0.75" is standard) is the same diameter as the pistons gas block, then yes you can install a piston system. Finding a good barrel is the tricky part of this build.

    3. There is a variety of opinion on the combination of AR15 & 7.62 x 39, some say they are great. Others say not so much. Main issues referenced are magazine availability/quality and difficulty feeding ammuntion. Scroll through the AR 15 section on the forum, there are several threads on this subject.

    I still want one, just have not pulled the trigger so to speak.

    Armalite has introduced a 7.62 x 39 upper, that may be worth checking out.

    Don't be afraid of direct impingement, it is a reliable system.
     

  3. Quentin

    Quentin New Member

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    Gatoragn pretty much nailed it above. From what I've read of others trying this, usually buying a complete DI upper, the biggest challenge is finding magazines that will feed 7.62x39 reliably in the AR magwell. I don't remember a piston build but suppose it would work as long as the gas impulse can be adjusted properly.
     
  4. GregTheHun

    GregTheHun New Member

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    The only thing that I'm not a fan of in the DI system, is that the gun has to kept a wet gun. It's not that I won't take care of it, but none-the-less...

    One more trick, can you make it lefty, with controls and round ejection?
     
    Last edited: Jan 29, 2012
  5. Gatoragn

    Gatoragn Active Member

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    I am not an expert, but I own a piston 5.56 AR and I apply the same amount of oil on it as I do on my DI upper. Also have a blow-back AR copy in .45 acp that works best when well oiled. I believe it is just the nature of the beast.

    Midway USA sells a left handed stripped upper. Lots of ambidextrous controls on the market today.
     
  6. GregTheHun

    GregTheHun New Member

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    Oh, I know you can make it left handed, but do you have the option of makin it 7.62x39 with a gas piston and left-handed?
     
  7. mjkeat

    mjkeat New Member

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    What are you wanting the x39 round for and what will it do in an AR that it won't do for you in an AK?
     
  8. Gatoragn

    Gatoragn Active Member

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    Installing a barrel and piston system on an upper is the same process, whether it is left or right hand oriented.
     
  9. GregTheHun

    GregTheHun New Member

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    Well, there's two things that I like about the 7.62x39 round mjkeat.

    One, it's ability to punch through some heavy duty stuff at close range... Which isn't so important now as when **** hits the fan.

    Two, price, cause its dirt cheap.

    I like the AR's versatility in the fact that it can have a lot of accessories and parts changes to allow different cartridges.

    Plus, parts are always easy to replace.

    And an AK is just an ugly gun.



    And Gatoragn, the caliber doesn't matter with left or right handed operation, I've heard some people talking about how you can either get a right handed gas piston gun in that caliber in gas, or left handed with DI and that caliber.

    But not both.
     
  10. Quentin

    Quentin New Member

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    Hey everybody's got an ugly duckling or two!

    I love my ARs but have to say for the Soviet rounds the AK is the way to go as there's no doubt that it works. I hope you can find what you want in an AR but with all those parameters you're beating your own trail.
     
  11. mjkeat

    mjkeat New Member

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    I agree ARs are more pleasing aesthetically but who cares, it's a firearm, a tool. The AK is a better choice for the round and you can pick up an AK for $400. Your other points are certainly valid.
     
  12. GregTheHun

    GregTheHun New Member

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    I just wanted to make sure, because I am a lefty and in that caliber with a gas piston operation vs DI, things seem to get a little confusing when trying to build your own. ^_^
     
  13. GregTheHun

    GregTheHun New Member

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    Ok, so, now I'm thinking about making it a right handed one.

    Someone made an excellent point about keeping it that way so if you had to check for jams, you never have to break your grip on the handle.

    Which is a good point, then I can buy ambidextrous safety switch, problems solved.




    Threads closed. :p
     
  14. HeftyLefty

    HeftyLefty New Member

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    AR-7.62 x39

    <1. Standard AR lower good to go. Most reliable magazines I've found are ASC brand. For me, flawless feeding. 5, 10, 20 or 30 rounders, specifically designed for AR platform with the 7.62 x39 (Soviet) rounds.>

    <2. I have: Adams Arms systems need a 0.750 diameter on your barrel. I used a mid-length system but carbine length should be fine too.>

    <3. Adams Arms systems - their Gen 1 - doesn't have an adjustable gas block. Be prepared to fine-tune with a heavier buffer. Some say the gas porting is off on every barrel but I haven't found that to be a problem. Using one from Black Rifle Arms. It's a better barrel than I am a marksman. Didn't measure the gas port but think it's 0.093".>

    AR with AK ammunition = pi**ing off everyone on both sides of fence! Economical AK rounds, superior AR accuracy! What's not to like?
     
  15. HeftyLefty

    HeftyLefty New Member

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    Yes. Easily. (Yes, and I have.). Just takes $$$.

    The *ONLY* parts different from a lefty AR to a righty AR are the bolt, bolt carrier and the Upper Receiver. In your case, there's no such thing as a "lefty" or "righty" piston set-up (that I know of) so if the correct "lefty" parts are sitting on your workbench, then it's just a matter of converting / integrating them all together.

    Providing the barrel (maker) of choice is up on their technology, the barrel extension should be OK with either right-handed or left-handed bolts slamming rounds into battery.

    Your Lower *can* have a left-handed or ambi safety selector, too - for convenience - and that's about it. (IMO, "ambi" bolt catches & magazine releases are pretty gimmicky - but if they work for you, fine.)

    I'm using a barrel from a company that's really into 7.62 x39 set-ups in the AR platform - and they make complete piston packages, too - just not for us lefty's ... Black Rifle Arms in New Smyrna Beach, FL. I'm using their 16", mid-gassed pipe in 7.62 x39.

    Agree or not, but Adams Arms in Odessa, FL is a tried-and-true performer when it comes to AR piston kits. They have two gas blocks; a "Gen 1", non-adjustable with a Pic rail on top - and their XLP that *is* adjustable but lacks the rail for your front sight.

    I've gone with the Gen 1 (p/n GB1-AA) because I like my front sight (a folding version) mounted on the barrel. The biggest risk with the non-adjustable gas block was over-gassing the system - but with a mid-length set-up, the reduced pressure vs. a carbine-length port was a gamble worth taking. My set-up works just fine!

    In addition to the non-adj. gas block, above, the other parts needed - no, I did NOT buy a complete kit! - are:

    Carrier Key Assembly (CK)
    Gas Plug (GP3)
    Bolt Spring (SP-BLT)
    Drive Rod (DR-P, DR-C, DR-M or DR-R - Pistol, Carbine, Mid Length or Rifle)
    Drive Rod Bushing (BS-DR)
    Drive Rod Spring (SP-DR)

    Depending upon your Upper Receiver, you may also need (I didn't):

    Upper Receiver Bushing (BS-RC)

    You'll also need a new "lefty" 7.62 bolt for your bolt carrier - and an "enhanced" firing pin. I sourced both of these from Red X in Minnesota.

    Remember, you're trying to set off centerfire ammunition with Berdan primers vs. Boxer primed rounds most of us are used to. This "enhanced" firing pin is a minuscule 0.010 or 0.015 inches longer ... but apparently makes a world of difference in reducing / eliminating FTF rounds from Soviet style ammunition.

    I think Red X also sells full "lefty" BCG's in 7.62 x39 for your AR conversion but you'll still have to swap out the standard gas key for the piston kit Carrier Key Assembly. (I already had a Stag Arms "lefty" BCG to work with.)

    I also started my build with a new barrel - not a retro-fit - so the excellent instructions & video Adams Arms provides on their website made installation a piece of cake - just follow them carefully, step-by-step and you'll be a happy camper.

    The absolute "hardest" step - for me - was removing the gas key from my Stag Arms "lefty" bolt carrier and re-installing that Carrier Key Assembly in it's place. This is the item that the drive rod contacts so you MUST install it correctly and securely. Screw this step up and you'll probably need a new bolt carrier and a new Carrier Key Assembly. But the gas port diameter in the bolt carrier is within an eyelash of the mounting nub on the Carrier Key (0.1875") so using a vise with padded jaws, VERY CAREFULLY & SLOWLY pressing this little item into place is pretty easy. Just take your time; think things thru before acting. (A variation on the old "measure twice, cut once" philosophy.)

    The rear-most bolt on the Adams Arms Carrier Key Assembly proved to be too long to allow the firing pin to be re-installed so I had to shorten it appropriately. (I chucked the bolt head in an electric drill and ran the threaded end over a fine file. Perfect ... )

    I've never installed a gas piston system before and I'm NOT a gunsmith either. Very likely, I'm not "smarter" than anyone reading this but I am smart enough to know what I want, how to get it (if it exists) or modify something to create what I need - and I have a strong mechanical & machining / manufacturing background on my side.

    To get up and running, I STRONGLY RECOMMEND you source ASC magazines specifically designed & manufactured to fit perfectly into your AR-15 mag well and feed 7.62 x39 rounds into your AR-15 conversion!!!!

    Good luck!
     
    Last edited: Aug 16, 2016
  16. fsted2a

    fsted2a Active Member

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    In the AR platform, there are 3 parts that are different between 5.56mm and 7.62x39mm, the barrel, bolt, and the magazine. All other parts are interchangeable. Shooting lefty you will need a lefty bolt and upper receiver, as far as I know. Adams Arms piston systems are the best known for DIY'ers. From personal experience with several drop in systems, if you are shooting steel case rounds, DI systems are less reliable than pistons on average. Most of the time if you are buying ammo by the thousand round case, the Russian ammo is cheaper than brass by a long shot. If you don't shoot that much, it may not be worth it for the piston.
     
  17. Ibmikey

    Ibmikey Active Member

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    Greg, Alternative is to dump the commie round which is no longer " dirt cheap" ( how much ammo do you normally consume each month? I normally am in the 500+ bracket). I have a couple of my AR's in 300 Blackout and love them ( you must reload to shoot lots of this cal.) i can shoot a thirty cal bullet in a total AR platform with a simple barrel change and not have a need for special mags or their problems.
    This post is my opinion only and you do what you want in the way of firearms procurement but why reinvent the wheel? PS: i too think the AK is ugly, but many lovve em'.
     
  18. Sgt_Skrb_25

    Sgt_Skrb_25 New Member

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    I say go for it. I love my build, I went with DI gas, not a fan of piston systems . But one thing to consider is the magazine dependability. I tried Every mag available and they all have feeding issues with 7.62x39. I finally solved the problem with Frankenmags. It's a half AR half AK mag . I have chewed thousands of rounds without mis-feeding. Try to find or make these. All of the available mags will have issues unless you run like 10-12 rounds in them . But if you want a reliable 30 rounder try to find these mags. ImageUploadedByFirearms Talk1473720250.060360.jpg ImageUploadedByFirearms Talk1473720263.225601.jpg ImageUploadedByFirearms Talk1473720271.733635.jpg
     
  19. HeftyLefty

    HeftyLefty New Member

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    Still, 7.62 x39 is about 1/2 the price of 5.56 x45 ........

    I have a .300 Blackout upper too. Love it - but don't re-load - so it has become an expensive paper-weight.

    Shooting .300 Blackout is "reinventing the wheel"; the 7.62 x39 rounds certainly aren't! That round is legendary post WW2 - probably the most popular .30 caliber round after the 7.62 x51 / .308 Winchester and / or the 30-06. By comparison, the .300 Blackout is still wet behind the ears. Simply no longer much support for it ....