I started out as a heavy bullet guy in the .375 Winchester. The 200 grain Sierra changed my mind. The 200 grain Sierra is a tough bullet and penetrates well for short bullet.
I always fall back to the 38.0 grains of Hodgdon 4198 load with the 200 grain Sierra which delivers 2,313fps and nice accuracy.
Alliant Reloder10x is one of the most consistent powders I have tried.
41.0 grains of Reloder 10 delivering satisfying accuracy and 2,250fps.
42.0 grains of Reloder 10 is just slightly less accurate at 2,280fps.
I have chronographed both loads many times and the SD's run right at 10 and 11 fps.
41.0 grains of Hodgdon Benchmark will just top the 2,300 fps goal with good accuracy. I am just not as happy overall with Benchmark or 322 in the .375 Winchester.
Good accuracy for me is anything in the 1 1/2" and under bracket. I have to work at it to shoot consistent 1 1/2" groups from the bench. If I slack my concentration a round will slip out of the group. Due to poor eyesight and in general close shots in the brush I use a large white bead. This does not help shoot small groups from the bench. I use large black poster board aim points.
As with all of the Big Bore Winchester cartridges we run out of case capacity at a COL of 2.550" just as we approach a maxim load..
