Finally got mine running, sort of. Made a brake for it. Recoils less, no copper deposits on the brake. Still not as loud as my .44 mag. revolver. Shoots 3+" at 100. Expected better. Only shot it 6 times so far. Might be the brake but not sure yet. Using 270s, moly-coated (at home-tumbler) with mag primer, & starting dose IMR 4350, per Hogdon reloading web page. I had to reload the new cases with an assortment of dies because the guy on Gunbroker I bought the .375 Ruger dies 2 weeks ago hasn't shipped yet. Anyways, I didn't resize the new brass but still got enough neck tension to hold the bullets from moving in the magazine from recoil. No visual runout of the bullet /case.
I'll know better when I get the right dies, & maybe try it with & without the brake. I'm thinking accuracy would be better if I speeded up the bullet a bit. Probably getting about 2500 FPS now. Some rifles like the moly bullets and some don't. I like breaking in a new barrel with them~kinda avoids copper deposits in the barrel.
What do you think?