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 Need some help building a 7.62X39 AR
OIF_Vet08-09  [Team Member]
12/18/2010 5:15:51 AM EST
My Dad recently purchased an AK-47 which got me interested in a rifle with more short range punch then a 5.56 bullet but that doesn't cost as much as say a 6.8 SPC or a 6.5 Grendel. Since 7.62X39 ammo is cheap and plentiful, I have started looking into building an AR for this round. I am already researching barrels, but as far as the other components go what else will I need? Do I need a dedicated 7.62X39 upper and lower or do I use a regular 5.56 upper and lower? I am pretty sure the bolt is different, but can I use a 5.56 LPK? I tried looking through the AR Variant section but there are not many posts covering this type of build. If I could get some info on what parts are different between this caliber and the 5.56 AR then I would be a happy ARFCOM'er
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man-of-many-guns  [Member]
12/18/2010 5:20:34 AM EST
You can expect to only use brass case ammo, As the chinese and russian polymer will foul the chamber and cause failures to chamber , stuck cases etc. AR chambers a designed with tight tolerences AK chambers will work with mud and sand in them. Just my view! As a qualified Armorer I know it to be true!
uscombatdiver  [Member]
12/18/2010 5:40:47 AM EST
At minimum (you are not going to be disassembling uppers to swap calibers) you are talking about a dedicated upper. You can use the standard AR lower but will need 7.62x39 AR mags. The parts that are different apart form the obvious (the barrel) is the bolt. Everything else is standard AR 15 parts. As far as ammo selection according to the 'armorer' you should only use brass, that is contrary to what I have experienced as there is no measurable residue left by the steel cased rounds and no variation in function. Apart from self proclamation I would be interested in round counts before the chamber gets so dirty from either steel or lacquer rounds that the system begins to fail. Thus far I have yet to notice, but maybe I'm not shooting enough rounds (it's a cost thing, that's why I'm now building a 5.45x39 upper which has no brass options at all). The one thing to consider is that the majority of 7.62x39 ammo is corrosive and a chromed lined barrel is ideal but not the only part(s) affected by this. I hope this answers the question and doesn't interject too much opinion. Good luck and like always, we love to see pictures of your finished projects.

Maybe this guy could answer the question since he's shooting a 5.45x39 in full auto (and 5.45x39 is only available in lacquer/steel casings). http://www.livevideo.com/video/CF8638F6050D4502A1D3535EA3E51E16/5-45x39mm-upper.aspx

Or maybe these guys:

http://www.youtube.com/watch?v=Aobg3wHr93g&feature=channel

Or this guy:

http://www.youtube.com/watch?v=2LpHkf2r_dk&feature=related
44Echo10  [Member]
12/18/2010 5:42:42 AM EST
The bolt and barrel and magazines are the only parts that are different from 5.56.

http://ar15performance.com/inc/sdetail/339 considered the best bolt made for 7.62x39
aceranch  [Member]
12/18/2010 6:12:40 AM EST
I only shoot steel cased in my 7.62X39 and have had no problems chambering or ejecting rounds. As others have said, the only parts specific to 7.62X39 are the barrel, bolt, and magazine. Everything else is the same as 5.56. One thing to consider regarding steel cased ammo is the slightly deeper set, harder primers.
MMcfpd  [Life Member]
12/18/2010 6:30:03 AM EST
I've had a few. The combos that work best are the LMT bolt with a Model 1 firing pin enhanced for 7.62x39 or the AR Performance bolt with a standard firing pin. Steel case ammo is not a problem with either of the aforementioned bolt/firing pin combinations.

C Products 10 and 30 round magazines work just fine as do the out-of-production but findable USA 20 round frankenmags:


As others have mentioned, a standard 5.56 lower is all you need.
OIF_Vet08-09  [Team Member]
12/18/2010 6:34:36 AM EST
After sitting around and thinking about this build I think I might try and build this as an SBR since the 7.62X39 round is good for CQB and little else. Who makes magazines for this round that fit in the standard AR lower? I also think I will install a gas piston since the ammo is generally pretty dirty. Who makes the best barrels for this caliber? Thanks for all the input so far.
MMcfpd  [Life Member]
12/18/2010 6:39:36 AM EST
Barrels I've used (in order of preference):

AR Performance
Model 1 (ER Shaw)
ArmaLite
Bushmaster

Any one of the above will do fine; the first three have M4 style feedramps while Bushmaster has their own "bigmouth" feedramp:


The magazines mentioned in my previous post all work with the AR magwell/mag catch.

ETA - I don't know if I'd bother with a piston; mine have all worked just fine as DIs.
OIF_Vet08-09  [Team Member]
12/18/2010 7:07:35 AM EST
Has anybody used the SI Defense 16" 7.62X39 barrel? Any thoughts compared to say Model 1 sales?
SI Defense 7.62X39 barrel
QuicksilverJPR  [Team Member]
12/18/2010 7:10:01 AM EST
Originally Posted By man-of-many-guns:
You can expect to only use brass case ammo, As the chinese and russian polymer will foul the chamber and cause failures to chamber , stuck cases etc. AR chambers a designed with tight tolerences AK chambers will work with mud and sand in them. Just my view! As a qualified Armorer I know it to be true!


All completely incorrect information. You can shoot steel cased ammo in ARs just fine and dandy if the weapon is properly cleaned and maintained...
MMcfpd  [Life Member]
12/18/2010 7:28:02 AM EST
I've never heard anything about the SI barrel. It is interesting that it has a 1:8 twist; all those I listed are 1:10 (approximately the same as the AK-47) as are all the others I've heard of with the exception of the older Colts that were 1:12.
44Echo10  [Member]
12/18/2010 7:46:31 AM EST
Originally Posted By OIF_Vet08-09:
After sitting around and thinking about this build I think I might try and build this as an SBR since the 7.62X39 round is good for CQB and little else. Who makes magazines for this round that fit in the standard AR lower? I also think I will install a gas piston since the ammo is generally pretty dirty. Who makes the best barrels for this caliber? Thanks for all the input so far.


7.62x39 magazines by C Products
OIF_Vet08-09  [Team Member]
12/18/2010 8:00:55 AM EST
Originally Posted By QuicksilverJPR:
Originally Posted By man-of-many-guns:
You can expect to only use brass case ammo, As the chinese and russian polymer will foul the chamber and cause failures to chamber , stuck cases etc. AR chambers a designed with tight tolerences AK chambers will work with mud and sand in them. Just my view! As a qualified Armorer I know it to be true!


All completely incorrect information. You can shoot steel cased ammo in ARs just fine and dandy if the weapon is properly cleaned and maintained...


This is why I want to install a gas piston kit on this build. Hopefully it will allow me to shoot the surplus ammo and not have a massive carbon build-up....which brings me to my next question. If I used an Adams Arms kit, would a 7.62X39 bolt fit properly in the carrier?
OIF_Vet08-09  [Team Member]
12/18/2010 8:27:12 AM EST
Clearly I didn't search hard enough on this forum....I found several threads addressing my topic Oh well, at least now I can ask all my questions without resurecting a six month old thread.
JFA  [Member]
12/18/2010 8:57:26 AM EST
About the only different uppers out there are the 50 beowulf and the Remington RAR. The 50 beowulf just has an enlarged ejection port, and not by much, because simply the cartridge is big and fat. Good one too at that. The RAR is a hybrid. The bolt is an AR10 bolt which is larger then an AR15 but it fits into an AR15 carriers. So the upper fits an AR15 lower, but it fits an AR10 barrel extension and although not quite as thick as an AR15 upper, it is thicker. Now the rest are all AR15 uppers of various configuration..for example Flat top, upper with handle, side charging handle, etc. So any AR15 upper will work for your 7.62x39 both the standard and the M4 cut feed ramp one.

Now for utter reliability and guarantee firing of even hard primers, included all the steel Wolf ammo, and with more accuracy then an AK style rifle, it's very hard to beat a SKS preferably the Yugos. The Russians are pretty nice too.

With that said I build myself a 7.62x39 upper using a DPMS 20 inch heavy barrel which was made by Wilson. The barrel appears well made and it shoots really good. I don't shoot the steel cased ammo or hard military primers so I've had no problems with it. The biggest gain with the AR15 in that caliber is the accuracy. Unless you have a barrel maker make you a barrel with a .308 groove all the 7.62x39 barrels are .310 groove because the ammo is loaded with that diameter bullet. If you reload there are a few .310 bullet maker out there and if you're strictly going to be a reloader only I'd highly consider the groove of the barrel be .308. I believe when Ruger came out with their first Mini 30 it had a .308 groove but they have since changed to .310.

One last thing the bolt has a larger opening in the face for the 7.62x39, but it still fits the AR15 carriers....so all you need is a barrel, bolt, and magazines.

Good luck with your build.
jasonusvi  [Team Member]
12/18/2010 10:50:41 AM EST
Hard to beat the price of 7.62x39 ammo but I think 300BLK (7.62x35) has largely supplanted the need for AR47. Given 223 parent brass and surplus 30cal projectiles, reloading for 300BLK is already cheaper than for 6.8 or 6.5. Supersonic 123 grain ammo is going to be released with an msrp of $12.99 and likely come down from there. You don't need to screw with a dedicated lower or mags of questionable reliability... just use Pmags. Also uses your 5.56 bolt so don't have to worry about concern that the larger bolt face on 7.62x39 will cause early failure. 300BLK provides similar performance and is probably even more efficient out of shorter barrels than 7.62x39. ETA: Also launches subsonic 220grain projectiles quietly through a can. I found a load that reliably cycles my subsonic surplus 175 reloads and got some cheap surplus 145 grain tracers for additional fun.
OIF_Vet08-09  [Team Member]
12/18/2010 6:11:14 PM EST
If I reloaded I would check into the new calibers coming out like .300 Blackout and .300 Whisper, but since I don't reload (yet) I plan on just sticking with readily available calibers. I am leaning towards making this an 11.5 build just for shits and giggles. Since I also have a .308 build planned I don't need this 7.62X39 build for long range. Gosh this BRD is intoxicating....
QuicksilverJPR  [Team Member]
12/20/2010 5:09:23 AM EST
Originally Posted By OIF_Vet08-09:
If I reloaded I would check into the new calibers coming out like .300 Blackout and .300 Whisper, but since I don't reload (yet) I plan on just sticking with readily available calibers. I am leaning towards making this an 11.5 build just for shits and giggles. Since I also have a .308 build planned I don't need this 7.62X39 build for long range. Gosh this BRD is intoxicating....


I'm becoming a fan of the .300 AAC BLK (Blackout). I would like a barrel to play with now...
MMcfpd  [Life Member]
12/20/2010 7:55:26 AM EST
Originally Posted By QuicksilverJPR:
Originally Posted By OIF_Vet08-09:
If I reloaded I would check into the new calibers coming out like .300 Blackout and .300 Whisper, but since I don't reload (yet) I plan on just sticking with readily available calibers. I am leaning towards making this an 11.5 build just for shits and giggles. Since I also have a .308 build planned I don't need this 7.62X39 build for long range. Gosh this BRD is intoxicating....


I'm becoming a fan of the .300 AAC BLK (Blackout). I would like a barrel to play with now...


Noveske for $455; I'm tempted, but not that tempted.
Forest  [Moderator]
12/20/2010 9:31:01 AM EST
Originally Posted By OIF_Vet08-09:
. I tried looking through the AR Variant section but there are not many posts covering this type of build.


Did you try looking in the Caliber Specific FAQ section? Perhaps under 7.62x39?
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