300RUM, with muzzle break on it shoots 2.5-3" groups. Muzzle break off, it shoots 1.5" groups, but also shoots 5" high. This is using Hornady factory ammo 220 eldx.
a 5" POI change isint normal. I install hundreds of brakes a year and normal shift is within 2-2.5" usually 1.5" or less even on brakes with top ports. Make sure there isint any contact from the bullet and also make sure the brake is tight and threaded all the way down bottoming out on the shoulder of the barrel not the last thread or two.