Bought a 7.62x39 Colt Upper a while back and am now going to get to building it. Whole new animal to me. Can I mate a standard AR lower to that upper using standard AR .223 mags? Sorry, but I really never followed much with the soviet round for the Colt AR. If this is a simple question....then please forgive the new guy! I have a couple different lowers I was thinking of using. But, I guess another thing is, does it have to be an A2 type lower to match the A2 upper? It's the 16" Upper W/A2 sights. Probably never offerd an A3 upper in the 7.62x39...huh?
      Wel, after you stop laughing at me...just kidding....right?, give a new guy a little help on this build. Thanks!  

Can I mate a standard AR lower to that upper...

Yes.

...using standard AR .223 mags?

About 7 rounds will work; C Products has new production 5 and 10 rounders, and 30s will be available "soon."

...does it have to be an A2 type lower to match the A2 upper?

No.

Quoted: Can I mate a standard AR lower to that upper... Yes. ...using standard AR .223 mags? About 7 rounds will work; C Products has new production 5 and 10 rounders, and 30s will be available "soon." ...does it have to be an A2 type lower to match the A2 upper? No.

     Thank you MMcfpd!! I appreciate the help!

You know, now that I think about it, I'm not sure about the pivot pin size that upper takes. Someone else here might know. If it is a Colt large pin there are adapters to use it with a standard lower. Are the front and rear takedown pin holes the same size?

I'll check...

But, what happens if the lower is MARKED .223 and you use a 7.62x39mm upper on it?

Does OP have to buy a new lower marked 'multi?  

It doesn't matter what the lower is marked as, you on the other hand do need to know what's on top so you don't load the wrong ammo.

It's nice to have them marked the same but NOT required.

My pre-ban Colt 7.62 has a standard .250" front pivot pin.

I just found out today that 7.62x39 existed in an AR form. Now i am on a mission to build one. I don't know anything about AR's

So let me get the straight, all that matter is that the upper is 7.62 and beyond that the lower deosn't matter, but i will have to find suitable mags to fit the lower?

Sorry about the dumb questions, i know nothing about AR's, i am an AK guy by nature but i am trying to spread out a little.

Upper is what is different.

Standard 5.56 AR mags will reliably feed 5-7 rounds.

C-Products makes a dedicated mag (high capacity still to be delivered).

Just built a 7.62x39 myself.  You can put that barrel on any upper A1, A2, or A3.  If you put a 7.62x39 upper on a .223 lower and pull the trigger, it goes bang.  The sky doesn't fall and the ATF does not start rappelling from the black choppers above.

Oh, and Model 1 Sales also sells dedicated mags as well, but still only 5's and 10's.  But if you're deer hunting or something, most states require no more than 5 cap anyway.  Lot of reloading for just blazing away for the heck of it, though.

Have fun!