tired of idiots
If you want to keep the upper,lower carrier bolt and magazines, look into the supersonic loads of the 300 whisper or 300/221 fireball. The hotter loads are close to 763x39 and you can have a MUCH larger selection of 308 bullets.
If you don't mind reloading, the 6mmX45 conversion is just a barrel swap. It uses 223 brass necked up to 6mm. My father in-law has the 50 beowulf upper and likes it. Pretty much if the round will fit in the magazine and there is a compatable bolt for it, someone has made an upper in that caliber. They're like Lego guns in that its easy to change out parts.
Gunco Addicted for life
i may have to build a 7.62--the old russian round is just too versatile to not use in a AR. i might even try one of those quick-change barrel kits ? anyone ever use one??