Not Sure What Caused This

[Lefty Trigger]

Remeasured. Loaded is .2815. Fired is .2875. As I said in the first post, I backed off the sizing die one full turn. Do not think it is a head space problem. This was not a light load. I will have to fire the Winchester brass to see if this is different.

Is that a brass neck diameter? If its a neck diameter the chamber is a little large in my opinion which would lead to the soot issue. I have an old Mauser military barrel that is large necked and it will actually split the necks if I dont keep them annealed. You should only have about .002 to .003 neck clearance from loaded to fired.

 

[Jennb]

Had a rifle re barreled a few months ago and I get this soot deposite on the cases. Never had this happen to this degree before. I backed off the reloading sizer a full turn so there was plenty of positive head space. Did not help. Am using Nosler brass and it seems to be thinner than the Winchester. Loaded Nosler cartridge measures 0.28275 ". Fired is 0.28175". Nosler brass measures 0.0135" in the neck wall thickness. Winchester measures 0.0145". The reamer print says 0.2580". Do not think the Winchester brass does this soot thing.
I think the chambering job is okay. Within .0005". Loaded round is .0075" less than fired case. Does not seem excessive. Does this with all powders tried.
Question is, am I just being over the top with this? Cartridge is .257 Ackley.

Look at the rings on the brass at the body/shoulder junction. You definitely have a chamber or sizing problem. You also only want about .002 on your shoulder.