Although "mega-overkill" for most purposes, it's a great cartridge. Sorta like a scaled up .223Rem.
I've used most of the appropriate powders and have found that the original application I obtained the rifle for to be the best.
Like you, I got my .300RUM on the cheap as the rifle was used, at a pawn shop and wouldn't sell due to the cost of the ammo. I deliberated on getting it for a long time. I fianally got it and I've been pleased with it.
My favorite load (rifle's too) is really a suprise. I've found that the best all-around powder for 180gr and heavier bullets is the WC-860 surplus .50BMG powder I obtained from Widners for $50 for 16lbs !!!
With neck-turned "match prepped" Remington brass and Fed 215 primers I'm getting 3,350fps from 107.0gr. This noticeably exceeds the factory ammo in many cases (claimed 3,250fps). Best accuracy has been with 105.0gr for factory duplication, and with the "garden variety" Remington 180gr Remington Corelokts. This bullet IS in fact suitable for this cartridge based on my "example of ONE" in its application on a 120lb doe I blasted with it at the great range of 40yds. The bullet held together and completely penetrated the torso of the deer on an intended raking shot to see if it "would" hold together. It performed in an exemplary fashion.
I've also tried the other "suitable powders" from H4350 thru "Retumbo". My personal favorite amoung these was/is Reloader 25. Retumbo is defintely the velocity King, but RL-25 is slightly more accurate and versitile.
If going for Antelope, I'd either use the aforementioned 180gr Corelokt, or the 150gr Corelokt or 150gr Nosler partition. RL-25 is much faster than the WC-860 with the 150's giving over 3,500fps (about like shooting 55gr bullets in the .22-250). A full case of WC-860 gives only ~3,350fps with the 150gr bullets, but accuracy is sub-moa if bullet is up to it.....
I've had good results from the few 200gr Nosler Part. factory loads I've shot through the gun. (20rds obtained with the rifle. Accuracy was excellent-matching the best I've obtained with the 180's, or even better...)
However, This rifle being so much heaver (a Savage M110 w/Simmons 3-10X "44mag" scope @ 9lbs) vs. my Remington M7 in 7mm08 @ 7.2lbs w/ Leupold 2.5-8X Vari-X III, it doesn't see much use except at the Range.
My next project over the next year with this "Monster" will be to develope some reduced loads with the 180's at '06 velocities. Accurate and Hodgdon/IMR have some interesting data for XMP-5744 and SR-4759......
p.s.
With the surplus powder and bullets I obtained in bulk before the huge price increases, I'm shooting this monster for less than I can reload for a .308 or my 7mm-08. Bullets ran me about 9cents each, Powder is about 15cents as shot, and primers about 2.5cents.. neglecting the cost of the brass this is 28cents as shot.......Not bad for one of the hottest cartridges on the scene these days....
