Recently I purchased a used upper assembly from an individual at a local gun show. It is a complete A1 with teardrop forward assist, 16" CAR liteweight 1-12 twist barrel, bolt carrier is a properly machined to AR spec, M-16 with a "C" stamped on it. The upper has "E  K " in the side recess under the rear drum sight. The barrel has no markings that I can find, but it appears to have a chrome lined bore/chamber(sure is shiny, how do you tell if it is chrome?) I put it on a pre-ban Bushmaster lower and shot it at the range and did about as well with the irons as with my other AR's- 4-5" @100 yds( I'm pretty bad with iron sights!) The receiver seems a bit looser on the front pin than my others, I believe it has been used a lot, but I am satisfied that it is functional. I am curious as to the manufacturer of the upper and the barrel. Also, I noticed Bushmaster sell an adjustable pin to help take up slop, can you use it in the front? Their website does not specify. Any help on this would be greatly appreciated!
P.S. I got it for $225, seems like a good enough deal to me!   Lee.

Your upper receiver is a Bushmaster.
[url=www.biggerhammer.net/ar15/upper/]Bigger Hammer[/url]
the barrel,however,is probably not.Bushmaster generally uses all the correct barrel markings.
An "M-16" bolt with a C is probably Colt.
Also check [url=www.jpar15.com]JP Enterprises[/url] for a slack reducing pin.
[:\]
ps with a B/BC/CH, you got a good price.

Notack, thanks for the info and the links!!
I am still curious as to how to verify a chromed bore/chamber?!? Lee.