Building a 7.62x39 upper...

[Rorge Retson]

From some reading I have been doing I gather that I can build a 7.62x39 upper for my AR, and it should function fine (while being more accurate than you average AK), is that correct?

Are there any specific guidelines for doing this correctly, or is it like with any other upper? Some questions I have:

1) Barrel - is an HBAR best? I'm looking at this one.
2) BCG - so far this one seems pretty good - anyone else have them?
3) What about mags?
4) Anything else I need? Different buffer spring?

Thanks!

[nick]

You'll need a stronger hammer spring for the Russian ammo. As for the mags, get the 10/30 ones, not 10 rnd.

[bruss01]

I built one, great gun. Look up my threads on it if you want some tips.

[slomofo]

Barrel and bolt is all you need. Mags can sometimes be finicky, but I've never had a problem with 10 rounders. I use 30 round mags loaded with 25 and that's all that works for me (more than that will get follower tilt), but in CA that shouldn't be an issue for you obviously.

[ratled]

I use ASC x39 10 rd mags and they work well. Kind of hard to get that 10th one in at first but they'll loosen up over use. I use standard buffers. A Wolffe HD hammer spring is must for import ammo

ratled

[kcheung2]

Unless you want the experience of a build (nothing wrong with that) it's cheaper to just buy a complete upper. I got mine from here:

http://www.radicalfirearms.com/category-s/2087.htm

The barrel is a heavy, and I used the same bcg you linked to, attached to a standard AR lower with no changes at all. I had no problems with Tulammo, and only a few light primer strikes with Golden Tiger.

Here was my post on it, post #16

http://www.calguns.net/calgunforum/showthread.php?t=1116565

I'm very happy with it's precision, it's almost as good as 5.56 and it definitely grouped much better than the AK I shot that afternoon.

[Metal Fiend]

I'm doing the same build.
I used this barrel / bolt combo:

http://www.deltateamtactical.com/762-AR-15-Complete-Bolt-Carrier-Group-and-Barrel-Combo_p_4158.html

And picked up the hammer spring from Wolff

http://www.gunsprings.com/index.php?page=items&cID=2&mID=1&dID=79

(XP Hammer Spring $4.99)

Picked up some ASC mags from the gun show last weekend

[mcisniper]

ASC 10rd mags, and make sure to get it head spaced. If every thing is within "mil-spec" extra power/enhanced is not needed but can ease the mind. The barrel and bolt should work, but head space it to make sure.

In my experience, you can almost expect one bad round per box of ammo. Wolf put out some really bad stuff a while ago and i was getting 5 to 6 bad rounds per box.

[jmpeal]

C product 2nd gen magazines worked for me, straight 10 rounders and 30s. Tried the ASC 10/20s and they had different feeding issues. The c product ones worked flawlessly.

Mine was from Radical also with the Seekins HG. I only shot MFS (Silver Bear) ammo and no issues with good accuracy. A fun rifle to shoot.

[EXTREMEOPS1]

Used aero precision upper half and an ARES Armor NIB BCG its flawless and accurate

[Cadre]

Not to high jack anyone know the right gas port size for a x39 pistol upper. Sent mine back to radical to fix.

[kenl]

Enhanced firing pin...check. +1 on the wolf extra power spring if you want to shoot steel case ammo, but you may want to upgrade your trigger group to offset the heavier pull. I've had good luck with the asc 10 round mags, but like other say, the 10th round is hard to get in. My rifle runs perfectly with a standard buffer spring and a carbine buffer.

I've had no misfires with the cheaper steel ammo after upgrading to the enhanced firing pin and the wolf spring over 1100 rounds ago.

Have fun with your new build. It's a great round in an AR

[MustangSteveGT]

Increased power hammer spring is a must with cheap steel cased 7.62x39. X39 has lower case pressure so anything you do to keep friction down on the contact surfaces helps. I.e. polishing contact points on cam pin bolt carrier rails, bolt. Areas that you would normally lube. Not a must, but 1 I built it helped. The feed ramps have to be wider and contoured to the fatter X39 cartridge projectile tip. Furthermore you may need to match the magazine to it. Regardless of who builds the upper, you might still need to tweak the feed ramps because there is no 1 uniform spec foe the X39 feed ramps across the board.

[Elwood_Blues]

Unless you want the experience of a build (nothing wrong with that) it's cheaper to just buy a complete upper. I got mine from here:

http://www.radicalfirearms.com/category-s/2087.htm

The barrel is a heavy, and I used the same bcg you linked to, attached to a standard AR lower with no changes at all. I had no problems with Tulammo, and only a few light primer strikes with Golden Tiger.

Yeah, throw a BCG and a CH and you'll have pretty sweet set up for just over 300 bucks. This looks like the same BCG as OP linked, but for 10 bucks less. http://www.joeboboutfitters.com/Radi....62x39-bcg.htm

[Click Boom]

PSA has a x39 complete upper on sale for BF that has really good reviews. I Was just looking at it..