Id try dropping the charge of powder to 40 , 43 and also try 45 grains of IMR 4198, (RL7 with similar charges,also works in many cases)
with a 350 grain cast bullet, gas check designs in my opinion and experience tend to provide better average accuracy,
use of a wad over the powder loaded firmly against the gas check, may provide some extra accuracy potential,
you may be amazed at the difference in accuracy.
yes Ive used at least 7-8 350-405 grain cast bullet designs.
the 400 grains are good the 350 grain cast gas check designs tend to be more accurate in my experience in the marlin 45/70 rifles
and magnum rifle primers are not always as accurate as standard rifle primers
you may be amazed at what a bit of experimentation in bullet seating, depth,
projectile sized and lube diameter ,and power charge can accomplish
( bullets sized and lubed .459-.460 tend to work rather well)
Ive tried many combos but in my experience , your generally not going to get anywhere near max accuracy at near max velocity
but you you can get impressive accuracy through careful experimentation and taking accurate notes on results
https://www.midsouthshooterssupply.c...cks-1000-count
http://www.neihandtools.com/catalog/index.html
https://www.midwayusa.com/product/17...nose-gas-check