OK thank you. I’ll leave it. Cleaning has been been temporarily resolving the issue (several shots), but it comes back pretty quickly.
Currently, I'm thinking that is just coincidence.
Via your measurements, the rounds with heavy bolt lift are .002" longer than the ones without. Your loaded round is falling free, so you're likely not running into pressure from a carbon ring. Especially after only a few rounds since last cleaning.
If your fired brass that was heavy lift functions properly after sizing and firing again.....then I wouldn't worry about getting wrapped around why those rounds were growing longer. Especially since you've checked headspace with go/no go.
If they do stick again, get some more virgin brass of a different lot number and see if the problem repeats. As with the measurements you provided, there doesn't seem to be any obvious reason for pressure.
There is NO lead in the bore or throat. The bullets you are using have a solid base not open to show lead. That would be the only way to get lead in a bore from a jacketed bullet.
The carbon you are seeing is more of a burn mark NOT a carbon build up. YET. What you have in the chamber is a non issue.
New brass just seems to do this every once in a while. Just make sure to not go under a 10% or so reduction in powder from a max listed load. That will also give you pressure signs from erratic ignition. You also might want to use a different primer. The ones you are using might be a little hotter than other types.
The carbon you are seeing is more of a burn mark NOT a carbon build up. YET. What you have in the chamber is a non issue.
New brass just seems to do this every once in a while. Just make sure to not go under a 10% or so reduction in powder from a max listed load. That will also give you pressure signs from erratic ignition. You also might want to use a different primer. The ones you are using might be a little hotter than other types.
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