A while back I received 3 firearms from my brother-in-laws collection after he passed away. Among the 3 is an AR-15 configured like the original M16. Since I have a custom AR in 5.56, I am considering a different upper in a different cartridge. Right now, the top of the list is the 6.5 Grendel, only because I load 6.5mm bullets for a Mauser.
Any suggestions as to cartridge and brand of upper assembly?
