I am new to the LRH site and I've seen a lot of talk about 300 ultras, but I can't find anybody else shooting a .30-378 Mark V. I've had this rifle for about 6 months and finally settled on a load for it after a lot of trial and error, from trying 5 different powders and bullet combos. There really isn't a lot of load data out there for a true long range load in this caliber.
My load is using Reloader-25 to push a Sierra MK 240 gr. at 3050 fps. This is very close to the pressure limit and I went as high as 3160 while "pressure testing" the recipe. The rifle is a Weatherby Mark V standard with the 28 inch barrel, plus the brake. I do not use the brake, and although it was very effective in reducing recoil, the inherrent loss of accuracy and the muzzle blast are not required (in my opinion) for what is still considered a "standard size" rifle. I know if I wanted to use the brake while out hunting with my buddies, I would soon find myself with much fewer friends. The scope is a Leupold VX-II 6-18x40mm with the long range varmint reticle. This load has proven to be slightly over a 0.6 MOA out past 1600 yards. I am compensating with 38 MOA adjustment to get out there.
I could find very little data for using RL-25 in this caliber. I think this powder shows a lot of improved performance in this "oversized" magnum cartridge.
Anyone else have any opinions on this caliber or shoot it regularly? I look forward to your replies!