I have a rifle that I can't seem to sort out. My Mosin is not liking cast bullets at all. I have always shot cheap jacketed surplus ammo through it with about 2 MOA results with issue sights.
I decided to make up some 312-185-1R Lee bullets because my mold drops a little over .314. I slugged the bore at .3125, and opened a .311 push through sizer to .3135.
I have tried these bullets with IMR 4198 at 1700 fps, which produced barn door sized groups, and a reduced 1300 fps load of red dot, which tightened it up to about a 4 foot group at 75 yards. I have tried ruining the oal everywhere from a mile long to way too short. There is no tumbling or keyholing, it is just slinging them everywhere.
I would like to get some direction here. I have been lucky enough with everything else I cast to come up with a working combination fairly easily. I can think of a million "could be's", but I'd like some help from all the years of experience on this board on the best places to start. I'd hate to spend a paycheck on a bunch of different powders and molds only to find out I could've sized them up .0005 or something and fixed it.