I finally found a factory load my 300 RUM does not like. It has shot everything I have tested around 1 MOA, with Nosler 200 ABs and 210 ABLR slightly better. I thought I would test some non-lead options. First try: a box of Barnes 190 gr VORTX LR. Grouped a legitimate 10-12 MOA. Shot ABLR before and after to make sure this was ammo related only. As a side note, or maybe related, the cases had some small dents (straight out of the sealed box) and the bullets also looked slightly pitted and/or tarnished. Anyone else have a copper bullet that works or doesn’t work in your 300 RUM?