New Shield+ PC. Ejected brass questions.

[scruffy]

New Shield+ PC is my 2nd striker fire pistol (previous Sig P365) and decades with S&W revolvers. Took the new Shield to the range for the first time today. 150 rounds total 100 Winchester 115 gr FMJ FP (flat point) and 50 Federal 147 gr FMJ FP. No hiccups FTF, FTF etc. The gun ran fine and was as accurate as I'm capable of. I did catch about 4 brass to the top of my head but that could have been bounced off the side of the lane separation walls. Scooped up some brass to look at later and:

1) I saw one of the Win cases had a crack. No bulging, no rough extractor marks on the rim and the mouth was round with no dents. Since I only grabbed about 10 cases I have no idea if this happened on any others. See 1st pic.

2) Some, but not all the brass had these witness marks from the chamber to varying degrees. Some had none. The chamber looks clean and smooth to me. What would cause this? Again no bulging or other anomalies. See pic 2

3) Last, the primer strikes are different than what I typically see. Are these normal for new M&P Shields? See pic 3.
Thanks for any insight.

 

[2wheels]

I collect my brass when I go to the range. Although I try to collect only my brass, I always seem to pick other people’s stuff as well. The pics you have look like poorly reloaded brass, possibly from another shooter.

 

[smithra_66]

Seems like that chamber is pretty rough.

 

[scruffy]

Seems like that chamber is pretty rough.

I looked at it with a loupe this morning after cleaning (I did not scrub the bore), It appeared to have a lot of little uneven splotches in the front 2/3 of the chamber lining up with where the marks are on the brass.

I used some Birchwood Casey lead free polishing cloth wrapped around a nylon .45 bore brush and wiped it all out. In five minutes the bore now looks smooth.

The cloth had what resembles a waxy/shiny looking dark brown hard resin on it. No more in the chamber. Not sure what it was or where it came from, but its gone. Going back to the range to verify tomorrow.

 

[scruffy]

I collect my brass when I go to the range. Although I try to collect only my brass, I always seem to pick other people’s stuff as well. The pics you have look like poorly reloaded brass, possibly from another shooter.

Thanks, I thought that also. Very possible except the cartridge headstamp was the same and the primer dent looked like my others. I'll keep an eye on it.

 

[Kp321]

The primers show firing pin swipe, very common on short barrel pistols. The barrel is unlocking and dropping while the firing pin is still in contact with the primer. Weak firing pin retract springs are the main problem.