Quoted:
I just got my Fulton Armory upper milled (on Friday) to take the G3 mags to use with my CMMG lower. Hoping to get to the range this weekend to try it out and I'll try to post a range report.
Please do. I am glad you are being guinea pig on this.
To the OP. If you are trained up on AR15s, or if you intend to run a scope, go AR10. I recommend Armalite. Mag prices arent' that big of a deal. Two of em. Course, I haven't got around to shooting one of them yet. It is my understanding that Armalite has better QA than DPMS.
My dad got a M1A. It was a jammomatic out of the box, recent production, but he sent it to them & now it runs like a top. There are some QA issues, but they will make it right. His is so heavy though. Make sure you get the lighter profile barrel or your MBR will be a Main Bipod rifle. He has the rails & the VLTOR stock. He does have solid top rail that goes from the back all the way up, it is a good scope mount.
The G3 doesn't just leave flute marks on the brass, it beats up the case rim pretty bad.