7.62x39 AR - getting it to run reliably

I got bored with 5.56 and only wanted one .450 so I built a pair in 7.62x39. One 16" carbine and one 10.5" pistol. Aero Precision lowers, Davidson Defense uppers. QMS trigger. I waffled between the x39 and .300BO but decided to go with the cheaper ammo, that is also shared by one of my AK's and my SKS. After about an hour at the range spent just fighting that carbine to get it to run I started to regret the decision. But then I decided to embrace the challenge.

What I found in my, ahem, troubleshooting.

First, you absolutely have to find reliable magazines and a good silicon based lubricant for them. There aren't many choices but I found the CPD seem to slide better than ASC. Also, probably not a great idea to go beyond 20 rounds. For starters, I think the pronounced curve of the 30 round mags looks goofy. Second, none of the 30 round mags I tried could be made to function reliably. Nothing helped. With the 10 and 20 round mags, it also helped to smooth out all the corners on the followers with a small file and some sand paper. I also ground a smooth curve to the front lip of the magazine body to prevent the case mouth from hanging up as it was chambered. That last made a huge different in feeding.

Second consideration is ammo. Once I got the mag issues sorted out, both would run generic steel cased ammo, Tula, RAS and WOLF without issue. The accuracy however, was not spectacular. a little better than my AK, not as good as the SKS and nowhere as good as the higher end AR's in 5.56. I went ahead and purchased several hundred rounds of PPU FMJ, some Red Army Elite FMJ, a couple boxes of Hornady match and a couple boxes of Fiocchi and the groups tightened up to a little under 2 inches at 100 off the bench. These last examples are boxer primed brass that I specifically bought to be able to handload, but unfortunately reloading for the x39 has become cost prohibitive since .311 projectiles are more expensive than a complete mil-surp round. Stupid.

In any case, I hope at some point to be able to exercise my dies and dial it in a little tighter than factory with some nice handloads.

So the moral of this story is that you can get an AR chambered in 7.62x39 to function reliably and hit consistently.

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7.62x39 AR - getting it to run reliably