Dakor,
Have only had a chance to test one load using the 300 gr Sierra Matchking. Topped out at 110 gr H-50BMG for 3050 fps with e.s. in the single digit range.
Was hoping for a little more velocity but the Sierra bullets are really fat for compared to most 338 bullets.
Richard Graves is making me some true .3380" 300 and 350 gr Ultra Low Drag bullets to test out. Hoping for 3150 fps or so with the correct diameter bullet for my throat. If they shoot and I am sure they will, I will probably lengthen the throat to allow bullet seating to the base of the neck. This will free up nearly 10 gr capacity with this bullet.
I ordered the reamer with the throat I did becasue I wanted to be able to chamber big game rifles in this round using conventional big game bullets.
One interesting note. My fireforming loads using a 225 gr SPBT are clipping along at 3350 fps with just barely enough pressure to fully blow out the Wby shoulder to its new 35 degree angle.
I would imagine with a little tweeking and testign of powders, the 225 gr Accubond could easily be driven to an honest 3500 fps out of the 34.5" barrel.
Accuracy wise, the top load with the 300 gr Sierra is grouping in the 1.4" range ctc at 500 yards. Not bad for the first load through the rifle. Will get her down to 1" or under at that range I am sure with a little testing and with Richards Wildcat Bullets.
If youare shooting the higher B.C. bullets you may need a 1-10 possibly but I doubt it. The 1-12 should handle anything up to a 300 gr Sierrra SPBT.
Personally, my new favorite bullet in the .375 bore for shooting out to 300-400 yards is the 260 gr Accubond. Love this bullet.
Accurized a 375 RUM for a customer and developed a load with this bullet for him to hunt Montana Elk with. Driving it to 3100 fps with top loads and getting 1/2 moa grouping out to 200 yards and 3/4 out to 400 yards. Very impressive bullet adn shoots pretty flat for a 375.
I'll stick to my ladies rifle for long range shooting though, do not want to toughen up my shoulder to much with those manly rifles.
!!!
Good Shooting!!
Kirby Allen(50)