450Bushmaster.net

New BCA upper...First time shooting today. Everything seems to function fine. No charging handle to the teeth, bolt stays back after last shot, fed and ejected each of the 5 rounds I shot. Only shot it 5 times since it was mainly to check function. Plus I had the upper mounted on a pistol lower with the blade arm brace.

Anyways, after picking up my spent casings, I looked over them. Upon inspection I noticed about 1/3 to 1/2 way around the rear groove by the rear end, that there seems to be black sooty type stuff. I also noticed a few scratches on the brass going from back towards front. I did use lots of slip 2000 oil on the BCG before firing the first shot. Could the soot film be burnt oil? Blowback from gasses for the function? Anything I should be Worry about? Thanks!!
****Edit****
After looking a I can see a little of the residue down the side of the case leading to the ring. A few don’t seem to hv as much, so maybe it was clearing up?

Full pics available in these links
https://i.imgur.com/K5XcN3v.jpg

https://i.imgur.com/nh5lPm8.jpg

I’d say the goo on the base of the shell is an abundance of oil mixed with carbon blow back. The scratches are likely from a burr in the chamber. Chuck a 410 bore mop in your drill with some metal polish, and lightly polish the chamber. I’ve done this on one of my BCA barrels with great results.

I’d normally say to send it back to BCA, but polishing a chamber is easy. As long as everything else works right, I wouldn’t think twice about polishing.

Soots normal on my factory bushey with most any load.

Scratches could be chamber, feed ramp, or lips on mag. I'd dehorn the mag first and see if that helps.

Al in Mi wrote:Spots normal on my factory bushey with most any load.

Scratches could be chamber, feed ramp, or lips on mag. I'd dehorn the mag first and see if that helps.

Forgot about the mag. I've had to debur some feed lips myself.