Recently had a 1911 build completed using a Caspian slide and frame.  I had the pistol smith fit and install a Nowlin barrel, and he had to finish ream the chamber.  I have put about 600 rounds thru the pistol, and I am getting half-moon powder burns down one side of the expended case.  This occurs with factory ammo, hot reloads, mild reloads, and different brass manufacturers.

 

 

I have a couple of questions:

Is this something to be expected out of a match chamber?

Is the chamber out of spec (excessive headspacing)?

 

http://www.nowlinarms.com/product-info.php?Nowlin_Gun_Barrel_Parts-pid190.html.

Have you measured the casing to see if it has a bulge ?

 

chamber check a round also and make sure it does not stick out of the barrel. 

As previously said you can check the headspacing yourself with an empty case...but that soot is a symptom of the brass not expanding to seal the chamber. My gun does that too and under normal circumstances that's a nonissue as long as she still shoots well.

 

I don't have a match barrel though, I suppose if the chamber is cut a little oversized you could have more space to leak gasses but on the other hand if its too tight you'll have jams. I'm not sure how you'd measure that without a hole gauge or bore mic though.