I put a caliper on one of the bullets, they measure .4525", I tried it in 4 different 45-70 bores, it dropped down the bore of two of em, one of the others took a little thumb pressure to push it in the bore, the last one was tight enought that I didn't want to push it in for fear of not getting it out.
So it depends on the bore how well it would shoot in a bore meant for a .457"-.458" bullet.
Tim