Quoted:
I thought colt's were not reknown for their fit and finish?
Not entirely. lol
Overall quality? Yes. But with fit/finish, they're kinda hit and miss. Back when my family had the gun shop, we would only get in 6-8 of them at a time, but there would always be one or two where the finish basically looked like shit. Most looked pretty good, but not all.
I'm pretty picky about finish (one reason I own no Colts at this time), but I couldn't care less if the upper and lower has a little wobble. Doesn't hurt the accuracy at all. Plus, part of the beauty of the AR platform is being able to use different uppers on the same lower...you'll never get one lower to fit perfectly with multiple uppers, and I like the option of using multiple uppers, so I just ignore it.
If it's really bad, you can throw an accu-wedge in, but those things are a big pain in the ass when you're trying to pop the takedown pin out. I bought one and ended up throwing it away. lol