I cut the chamber.... Never cut a bad chamber before in 40 some guns.... Guarantee its better than the factory chamber was lol Thompson center used revolver reamers to cut the chambers in the 357 mag barrels.... They cut a lot of bad chambers early on but this was done on a lathe all indicated in with a ptg rifle reamer..... I'm thinking the last time I had this problem I took the forend off and it went away but it's been a while since I shot it. I couldn't get it to stabalize the 200 ftx when I messed with it last. It would shoot one hole (couldn't even tell there was more than one shot) at 50 yards and at 100 it could barely keep them in an 8 inch plate... I got frustrated and didn't have the money for another box of bullets in time for gun season so I quite messing with it.... In my digust I apparently forgot. Though it would string even before I cut the chamber bigger with hot loads.... Did fine with a 158 at 1000 though