I need some help. I have a Cooper Excalibur in 28 Nosler with tally bases, Vortex PMR mounts and a vortex viper pst ii. I have shot the nosler 185 Match, 175 ABLR, 160 AB and the Hornandy 162 Eldx and the smallest group I can get out if is about 3 MOA. Double checked all the mounts and connections etc. I have followed the break in instructions. I’m trying to rule out it being the gun, so is there any loads that people with a similar set up have found that works? Any help at all would be awesome. Thanks!