I want to develop some cast bullet plinkers for my Ruger #1 375. I went to the Lyman manual and loaded up some Unique loads with 16 to 18 grains, no filler. Group at 50 yds clusters at about 3 inches, with 2 flyers out to about 6 to 7 inches (ouch). This gun shoots at 1 " or less with jacketed bullets. Tried a load (If I remember), 32 grains of 5744, again no filler. This load stunk! some of the shots were not even on the paper!. Am I pushing these too fast (I'd estimate 1600 fps)? Lots of bluish smoke and soot in the barrel. I cleaned a lot of gunk out of the barrel, no so sure what to look for as far as signs of leading. Your guesses on a next step would be appreciated. The bullets are 249 grains, no gas check, made by National Bullet co. and seem to be well made.

Aladin is on the money, but I'd like to add a little.

You're caught in a whipsaw. Those plain base bullets won't take much of a charge under them. That huge case is going to give you powder shifting problems with small charges.

I would suggest that you go to gas checked bullets and a powder, such as Red Dot, which has a lot of bulk for the weight. You just might try 13.0 grains of Red Dot under the bullets you have.

I have loaded for the .375 bore for a long time and have Schuetzen rifles in .38-55 and a couple of .375 Mags. For the Mags I suggest magnum primers and wad of a filler like kapox to hold the powder against the primer.

I load 45 grains of imr 3031 and the Lyman 375296 bullet and it shoots into 1.5 MOA or better. This is a gas check bullet and the alloy is linotype.

I have not loaded plain base bullets in the magnums but with a light load of a powder like 4759 and the kapox filler they should be accurate. A old Lyman handbook calls for 20 to 30 grains of imr 4759 with a plain base bullet.

You have got to use the filler. Get some kapox from a old boat cushion or life jacket and weigh up a tuft of a about 0.7 grains. Eyeball this tuft and then just tear off pieces about the same size and poke them in the case with a small screwdriver.

This is the beauty of the .375's. They shoot cast bullets very well.

Don,

I use fillers. Have for years, mostly dacron. But I shoot cheap rifles and can change my own barrels if need be.

There have been enough credible reports of damaged barrels from fillers so I am wary. This is not a place for someone starting out shooting cast bullets to go.

No problem. I use cast in my Ruger No.1 Tropical all the time. With plain base bullets 17 gr. of Green Dot, or any like fast shotgun powder, will give around 1700 fps and groups into .6 moa. The key for accuracy is to use Magnum rifle primers. I don't use fillers!

You say you are using bought bullets; have you measured them, or your barrel, to make sure they fit? If the bullet is smaller than groove dia. it wont shoot. Also check for damage on the base edge; even the smallest nick will cause a flyer.

For velocities over 2000 fps VV N140 is hard to beat. That is with gas checked bullets of course.

Thanks for the help. I measured last nite and the bullets are .377 as advertised. I am using Federal 210 primers. Sounds like I should use the 215.