rebarrel job

http://www.castbulletassoc.org/view_user.php?id=2607>biddulph; I'd say stop using 2400, it is a fast pistol powder and punches the heck out of cast bullets with a high rise short duration pressure curve.

You have a long barrel and a middle of the road weight  bullet for the 375H&H.

IMR 3031, H4198 and H4895, H380 and H4831 are historically a top performers with cast bullets in the 375H&H

A case-full of H4831 about 73 grains will not overpressure a 300 grain jacketed bullet in a 375 H&H. That speed powder will burn efficiently with a non peaky pressure curve for cast bullets in your long barrel and about 85-90% case full of H4831 with your bullet should put you right where you want to be for a long range load. You cant over pressure load and harm your rifle with H4831 , it is a slow and easy powder to experiment with in the 375 H&H with cast. I use a Military surplus powder that is equal in energy per volume to H4831 and shoot nearly a casefull with the Lyman #375449 gas checked 264 gr in #2 alloy.

I use new surplus IMR7383 at $56/7# jug.pplus hazmat/shipping and worth it!, My source:

http://www.gibrass.com/gunpowder.html>http://www.gibrass.com/gunpowder.html

You can not overload with this powder and any bullet in the 375 H&H, velocities are respectable and pressures are low. It is an ideal and terrific powder for cast in the 375 H&H

Gary