Can anyone help out ???? I have a cmmg ar in 762x39 and I'm having a feeding problem the 10 round mags are A.S.C. and are made for the caliber how ever 10 round will jam double feed or will not pick up next round I put 5 rounds in its no problem 7-10 has the feed issue. Anyone have any tips or anything I can try. Please help thanks.

from my experience the 10 rounders are shit. Mine won't hold more than 5-6 and work reliably. even after grinding down the front so the cases don't get hung up when being stripped by the bolt they still don't do well.

Don't know about the ones made for 7.62 but I bought 8 10 round .223 ASC mags and had a problem feeding the first round off the top of all 8 fully loaded.
The other 9 fed fine.

I started to find that using a LULA to load the mags and after the tenth round used the lever on the LULA to compress all 10 rounds back and forth working the spring about a dozen times seemed to correct the feeding problem.  Now all of the new ASC 10 round mags feed all 10 rounds without issues.

Not very scientific but worked.  I think with the final 10th round loaded it put to much force on the feed lips of the mag and by working the spring a bit may have reduced the pressure just a bit to allow that first round to be able to be drawn off the mag completely into the chamber without the bcg riding up over on top of the round and getting jammed under the bcg.

I threw away or gun showed' my 7.62 mags and bought C products mags and it is 100% reliable.