I bought a 300 WSM
when Kimber came out with the 8400 Montana. About 2004. My first load data came from IMR Powder, Speer and Hornady sites. loaded up some loads and went to the range. I fire lapped the barrel with 30 cast gas check bullets and fire lap compound, (Lyman Data for Gas Check bullets.) Cleaned barrel every 5 round group. Cleaned the barrel then started with jacketed bullets.
150 gr. bullets got 1 3/4 in. group.
165 gr. Hornady got 1 1/4 in. Group.
180 gr. Sierra shot in 9/16 in. Group.
180 gr. Hornady inter belted got 3/4 in. Group.
My load for the 180 gr Sierra Bullet, Listed in original IMR data.
Case, New Winchester, FL sized, Trimmed, 2.090, champhered inside and out.
Primer, Winchester LR (Box said for Standard and Magnum Loads then.)
Powder, IMR 4350 65.0 Gr. Sixty Five.
Bullet, Sierra 180 gr. 30 cal. Spitzer.
Overall Cartridge Length 2.860
With this load the rifle shot a 9/16 in. 3 shot group at 100 yds.
I changed the bullet to a Hornady Interlock 3/4 groups, Became my deer load.
For my Big game load I used the same Case, Primer, and Powder Load and changed to NOSLER 30 cal. 180 Gr. Partition.
2 Caribou, 1 at 175 and 1 at 125 yards.
1 Bull Elk at 220 yds.
These loads perform the same with the Winchester LR Magnum primers since they changed from one primer, to their present, Standard and Magnum Primers offers.
Rifle, Mounts, Scope and Sling and 4 rounds of Ammo weighs in at 7 1/4 Lb. Makes for a great walking hunt rifle.