Thread: Marlin xt22 MVSR problem

Well, I believe the gunsmith is in the clear.
The marks on the brass are caused by imperfections in the chamber - which must have been there from the factory. There is no way for that damage to occur during a routine barrel threading job.

Basically, when you fire a round the brass expands to fit the chamber. If there are burrs or imperfection in the chamber, then the brass will expand to the shape of the chamber, taking on any imperfections. Those imperfections then mechanically lock the spent brass in the chamber which is what caused extraction issues.

I think its just a coincidence that the problem only surfaced after you had it threaded.