I was looking at the bolts I have one one of them is marked "C" another is marked "MPC" and a third has very long "C" that looks like it was made by perforating the bolt. One of my carrier assemblies has the same "C". Two questions:
1. Why the different marks ("C" vice "MPC")?
2. What's with the funny-looking C?
To help you understand, I've posted a few pics. The first is of four Colt bolt carriers. The one closest has the large C.
The second picture is of a bolt with the long C.
Yes, I've looked at BiggerHammer.net's AR-15 Barrel and Bolt Information
page. It's incomplete.