I have a colt HBAR and was wondering why it seems like you never see anyone building on a colt. Is there something wrong with Colt? Bought mine from Daves guns a few years ago and it's accurate, reliable. Never have shot another AR to compare it to.
Also in the name of saving life on the barrel I'd like to add an upper that I could switch out that has a shorter (than 24") maybe like 18ish. Something I don't care if it gets REALLY hot from shooting up cheep ammo. What upper would you go with?

P.S. Why Does it say 5.56 Nato on Barrel and 223 on lower reciver? I know about shooting 5.56 in a 223 is a no no but ok the other way around....right?????