Military is finally learning, and recycling. We just got word from our Munitions guys to save all packaging, crates, ammo cans, cardboard and styrofoam tray... recycling at its finest.
I've ran across that same issue on brand new Colt uppers, military, and they would gauge just fine but wouldn't hold a group for ****. We had to go back a rebarrel 9 M4's because of this. Quality Control in the past 10 years has defiantly declined for Colt but some how their prices keep going up.
Nothing wrong with owning both. just don't swap the uppers around thinking about a fun time. Confiscation of the weapon, fines, lawyers, jail time... Not worth it.
Think about a Glock 19 or 26, even used, they will still last a lifetime. They might be a little bit heaver then what you're looking for but its worth it. Also don't forget about the holster. most people forget about that and even if you don't get a Glock a Fobus holster is what I'd recommend.