Accuracy with 300 Win Mag.
I am currently assisting a friend who's developing handloads for a Remington XCR 300 Win Mag. We conducted a proper barrel break-in period with the standard of shoot-clean, shoot-clean for the first 20 rounds through the rifle. We were using Factory Winchester 180 grain Power Point ammo and with the the last two rounds obtained a group at .370 inches (we were also trying to sight in the scope too). We wanted more rounds before we counted that grouping but had run out of factory ammo by then.
So next was handloads. We used Nosler 180 gr. Solid Base Ballistic Tip bullets and Reloader 22 powder. We experimented with loads from the lowest charge of 74.0 grains to the highest of 75.5 grains according to the Nosler reloading manual. We also tried an OAL from .010" off the lands to 0.025" off the lands, with the tightest group coming from an OAL of 3.587" (which was 0.010" off the lands). This group was the tightest and only measured at 1.015 ". Factory ammo had an OAL of 3.340". Factory ammo also chronoed at 3020 fps and the 74 gr. handloads were 3060 fps.....so pretty consistant.
The owner is looking for the rifle to consistantly group at no more than 1 MOA accuracy....so obviously we were not happy with this performance. Our last thought was to load the bullets to the factory AOL and see if it can group as nicely as those last two factory rounds did when they printed at .370".
Has anyone here experimented with a 300 Win Mag and also with heavier bullets.....? Any help would be appreciated.