I have loaded for 300 WM many years ago . If you are trying to conserve component's then don't do ladder tests they tend to waste components . Use three shot groups initially . It may not help to use other peoples loads they may or may not suit your gun .
Start at 69 grains of AR2213SC behind a 180 grain bullet and work up slowly . Accuracy is more important than velocity so finding an accurate load at safe working pressure that functions through the action easily is the way to go and case life will be better . Seat slightly clear of the lands and with respect to max magazine length and proper magazine bullet tip clearance for reliable functioning and the magazine length and bullet length usually limits your seating length anyway .
Makes sure your sizing die gives enough neck tension so no bullets move in the case neck under recoil within the magazine .
This powder was not even available when I loaded this cartridge .
Don't load up more than 3 sets of 3 rounds per load change , less would work also . 3 groups of 3 shots is all you need to see which load shoots best .
Recoil will be an important issue for getting consistent results to asses groups . So good grip of the gun and proper rest and bag setup is important to control recoil consistently . Don't try and shoot a 300 WM free recoil , it's not a 6mm PPC . Don't try and test loads on a windy day .
Accuracy is also a function of projectile quality and construction so if the Woodleighs are core bonded they will not shoot as tight as an unbonded , generally speaking . Nosler Partitions have a complicated jacket process and that can contribute to less accuracy compared to a simpler target style jacket . That does not mean don't use them it just means don't keep wasting ammo trying to make hunting bullets shoot like target bullets . There is a point where you can't do any better and then just stay with that best load .
Good stock bedding system is important for a cartridge with some recoil so if the accuracy is just real bad stop wasting ammo and investigate the bedding and recoil lug . If everything is in place then reassemble and tighten action screws firm .
Hunting bullets are generally not as tight shooting as bullets made for target shooting .
300 WM is a cartridge that has competition type dies available for it so think about modernising if you are still using expander ball type dies .
Also belted cases can sometimes suffer from an expanded section just above the belt which can hinder chambering . It's because some dies can't get down far enough to size it . If you strike this problem then there is a special collet die to fix that
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