Mike, I didn't slug the bores on the Lancaster, just eyeballed how far the bullet would enter the muzzle compared to how far it entered a barrel I had slugged. The .452 bullet was selected for my Edward Lang boxlock which has tight bores. I had NfB loaded rounds using JHP in .452 and LFN in .458 left over from our Colorado trip and just tried those in the Lancaster. The larger .458 bullets performed better, but both loads would be fine for whitetail within 75 yards.