It can be tricky, Winchester 296, for example, is safe and efficient for .44 magnum with a 240 grain bullet and 24.5 grains of powder, but a reduced load, 22 grains, with the same bullet can give severe overpressure. If 296 doesn't fill the case it detonates, as opposed to a controlled burn. Again, my memory isn't guaranteed to be 100%. I used to cast and shoot over 150 pounds of lead a year but it's been a long time.
I just recently learned about CIA “salted” ammo used against the NVA. Wish I’d known about it while I was in RVN, must have been classified. There was even a phony published report on the unreliability of East Bloc ammo complete with photos of burst AK-47s.
Speaking of reduced loads, I have fired .375 H&H magnum with the case loaded half & half with smokeless and dry Cream of Wheat filler. It was a neat way to get acquainted with the mighty magnum by starting with reduced loads and building up to full factory loads. The rule was, never leave any air space in the cartridge case.