I always stick to the upper mid range loads with the 338 LM. For the 300gr SMK I am currently using 76. 4 grains of IMR 4350 When we had the somewhat recent powder primer shortage I found equally good results with 79.2 grains of Re 22. These are Sierra upper mid range load recommendations, The published velocities for these loads has always proven to be a bit on the high side for the Chamber dimensions I choose. The nice thing about upper mid range loads with this cartridge is that they provide a very large sweet spot of consistent velocity spreads over a large range of seating depths. and have found them to be highly immune to a fair shake more than modest barrel erosion. Now you have my secret sauce recipe! The 338 LM is a modest velocity cartridge by super magnum standards but its inherent accuracy is something that the big kids on the block have to prove themselves against. P.S. for obvious reasons I disclaim every load recommendation that has ever been written or spoke including my own.
I know youíre looking for 300 grain pill loads but thought I would throw out a 250 grain option for you for future reference now that IMR 4350 has come up: my load being 82 grains under 250 SMK with Lapua Brass using GM215 primers getting 2854 fps bors input. Iíve also had great results with 225 grain TTSX and 89.3 grains of Retumbo 2910 fps bors input.
Pic is a 15 round group with my usual WTF flyer above, 5 to 10 min cool down between shots bore cleaned after each set of five.
338 LM Brass, 215M Primers, 300 Grain Scenars, 88 grains of RL 25 @ 2700fps shots 1/2 moa for me out of my 26'' 1-9.4 twist Rock. This is a mild load but accurate- have loaded up to 93 grains w/o pressure signs.
All right fellers I got my brass prepped up, and I think I have all the powders at my table except retumbo. I going to use 300 sierras seated at 3.7925. I am going to try each load mentioned here 5 shots at 200 yds and see what happens. Should I clean bore after every 5 shots? I thought it took 2 shots to foul the barrel after cleaning?
Yes it will take a couple to foulÖ once youíve found your load, start keeping records of how your rifle responds (poi) between those first five; meaning clean cold bore, second, third etc. Some may disagree but itís a practiced habit Iíll probably never break. I keep a constant data book on all of my rifles.