Scooped up an AR15 yesterday day. (Thanks again Eric for not gauging on a hi demand item!) Its a Smith and wesson m&p15 lower, ease told the guts are from Spikes, and the upper is from Bravo. The lower is clearly marked with model and manufacturer. The only markings I've found on the upper is the caliber and twist rate stamped on the muzzle. And there's some stampings on the furniture. Nothing inside the upper, and nothing on the bolt.

Its got an ass ugly paint job on it I'm gonna strip off, would I find any markings on the upper/barrel printed on them (provided they don't get removed with the paint?)

Is there any areas of concern to look at before I shoot it? Or should I just clean it up, oil it up, shoot it and take things from there? I'm new to ar's, but not foreign to them having been in the army. I can rip one apart and put it back together, not not sure if there are any issues with one that didn't start life as one complete rifle.