I already slugged the bore and it is .368 groove dia. on the money. I just fired 5 rounds with a cast bullet that was .366, yes, I am going lead mining but not bad. The OD of the case necks is .392-.393 and the ID is .368-.369 as close as I could measure so it might be tight. That was with Lake City-72, 30-06 brass reformed. Wouldn't inside or outside neck turning a bit cure some of that?