think I' partially resize the case or use an unfired case with a little JB paste on it. take about a #6 brass machine screw 2 in long and bore out the primer hole to take that screw and secure it with a brass washer and nut on the outside of the case. puta gentle curve in the screw and work it in and out and back and forth. use the case as a lap to polish the chamber and neck. a fair amt cheaper than a rebore. I've read of 'smiths restoring chambers of auto loaders in the snowy regions of the north using this method. JB will clean out easily with patches and solvent. may have been stored a little damp and developed some red crud in that chamber.
