Tonight I tried out some loads using IMR 4831 pushing a 180 grain Nosler Ballistic Silvertip. This load was a bit more perplexing because the max charge varied depending on your source. My Lee book states 54 grains for the max charge, the Hodgdon book has 56.8 grains (compressed) and the Spear #14 manual says 59 grains (compressed). I played it safe and went with the manufactures recommendation of 56.8 grains as my max charge. I backed off by 7% and started loading from there.
This load can best be measured in MOB, or Minute of Barn, as that’s how they grouped. If you look at the targets, as the charged was increased, the spread got wider and wider.
I’m really at a loss to explain this, I just don’t know enough about ballistics to provide an adequate explanation. Perhaps a knowledgeable reader can provide an explanation….
I’m tempted to work up some loads based off the max charge of 54 grains as listed in the Lee book. Judging from the first target, that’s a very respectable grouping, even if it is off to the left.