My Savage M110 really likes IMR7828, and shoots well with the 180gr SST, though the Nosler 180gr BT's are a bit more accurate. (Goes for all my .30's).
I like 84.0gr of IMR7828 which from my 26" bbl gets 3,200fps. Accuacy is MOA for 5-shots. (Though I seldom shoot them, ususally 3-shots for saving the bbl.) You can go upwards to 86.5gr for 3,400fps, but accuracy really falls off and my gun shows sticky extraction. Not to mention the RECOIL.....
85.0 duplicates the Remington Factory loads for 3,250fps. I even believe the IMR7828's whats in them due to charge wt, and appearance of the powder on the one I pulled, though I wouldn't hazard a wager.......
For the 200gr bullet, I'd use Retumbo, given a choice. Though I really, really like RL25, at 93.0gr w/180's. Retumbo at 98.5gr though, gives 3,350fps and nice groups. 100gr is too hot for my gun and gave "spikes" of 3,500+fps.
"Yikes" is Right !!! recoil was fierce, needless to say.......
Lately, though, my RL25 has been going to the .257wby. 74.0gr gives a Hornady 100gr Spt 3,700fps. Much more tolerable than the .300RUM.
And a .300RUM "AIN'T a poor man's .300Wby, it's something MORE..... A horse of a different color, if you will.......!!!!! Closer to the .30/378WbyMag, only with more reasonably priced brass......
Pay close attention to the guns used in generating the loading data. Many are worked up using a 24"bbl w/o free bore (ie: the Lyman #48 manual). These give much lower velocity figures than a 26"bbl WITH a freebore. My Savage .300RUM has the same 0.375" freebore that they put on their .300Wby barrels, and hence the higher than "book" velocites..... It's virtually impossible to seat a bullet out to touch the grooves. Tried it with a 210gr Berger, just about .250" of bearing surface in the case neck. They shot better seated to 3.625" anyhow....
