+1 brilliant idea.
he finaly changed his mind he is now planning on getting an M14 and just upgrading the hell out of it. htat way he can have a taste of both worlds.
Might I suggest he get an M16a4 mod0 SPR it shoot 400 fps and is very accurate. He can mount a decet scope on it use it as a 'close ranged' sniper rifle and he can still put attacments like m203s, and master keys. If he wants he could get an extended barrel to augment accuracy.
Best wishes to your cousin and his potential rifle,