The used Beretta 45-70 DR that I recently purchased was said to be regulated with 300 grain handloads at 1600 fps and at very close range, it was effective on a 300 pound feral hog boar.
However, the regulation was not satisfactory from 50 yard bench rest testing. Further testing showed that each barrel was sub minute of angle accurate, so the gun should have potential. I booked an appointment with a proven gun maker to regulate the gun but that would be several months in the future. So, what to do now?
I examined several 20 round boxes of my commercial ammo stash and selected a few types to shoot to see if one would help determine a starting place for handloading experimentation. Of that, the first to be tried at the range was Hornady 325 grain at 2000 fps. This ammo is a proven killer of big game, but would not group well in my rifle.
The next in line was Remington Green Box 405 grain JSP. Voila!
Two R&L cycles and there appeared a 4 shot 2 inch group level with the Bullseye! It was 4 inches to the right and easily corrected with a sight adjustment. Th rifle is now shooting a good hunting group that can be adjusted for range as needed.
Yes, I was very lucky, but wanted to shoot 400 grain ammo anyhow.