So my dad has this Colt 7.62x39 AR carbine that he bought for me during the Clinton panic buy in 1992 or 1993 when I was a toddler. It was the only one left in stock, and he figured it would be a fun plinker and decent deer gun. The best moments of my childhood were spent wearing out that barrel. The barrel is now long in the tooth.
Assuming he gives it to me when I fly home in August, I will be left with a long in the tooth 7.62x39 Colt upper. I may buy a Colt lightweight upper to cannibalize. If I do, the barrel will go to the spare A2 upper, the flat top will go to my current A2 rifle, I will dremel down the sear block on my current A2, and it will get the M16 carrier. The 223 A2 carbine upper will get the half moon carrier, and I will dremel the A2 rifle sear block to fit the M16 carrier. The only problem with this plan is a trip to ADCO to get M4 feedramps dremeled into the barrel of the A2 rifle.