I purchased an A2 upper to replace the one on my PD trade in Colt 6520. It suffered some rack damage on the carry handle and I wanted to get that fixed. When it arrived I tried it on the lower and found that the anodizing on the Colt had turned purple-ish and the lower didn't match the new upper. At that point I reevaluated the swap anyways since I bought the 6520 as a beater, so tossed some Alumablack on the wear and called it a day.
Now I have a spare upper laying around and I'm trying to decide which route to go with it. I have a pile of stripped lowers in the safe so it's all about just figuring out a configuration. I'm stuck between either a 14.5" carbine length barrel and going with a 723ish clone for my SBR lower, or a 20" M16A2 configuration. Been wanting a 20" AR, but the upper has M4 feed ramp grooves. Anyone have any suggestions for govt profile 20" barrels utilizing m4 barrel extensions? Or suggestions on a different configuration to go for with this build? I have an older set of CAR 6 hole handguards, a pile of N/1 CAR stocks, and a nice colt 20" rifle handguard as well.