Neat! I like putting AR's together much more than shooting them. Often contemplated trading it all in and going to gunsmithing school so I could remain poor.
Do you put a caliber or other designation on it?
Best not to put the caliber because you can swap lowers to many different uppers of different caliber. The caliber should be on the upper. I have more uppers than lowers so I just grab a lower and push in the 2 take down pins and go