The bullet nose design is the key. I have shot standard nose .45ACP bullets and then shot Keith design bullets with a sharp shoulder just below the truncated nose cone and the holes for the Keith design are noticably larger and the taper nose standard bullet holes are smaller and not as well defined (just pushed through not cut through). dmurphy is correct.NOTE: I will add that I have recovered only one bullet from an elk and it did not have any rifleing marks but the charge was a low level one that probably did not expand the bullet as it also keyholed when it hit the elk. Interestingly enough it passed through the heart sideways and lodged in the far ribcage. Bad load and bad bullet performance but it killed the elk. Still had the plastic nose cone piece in place and the bullet was only slightly flattened on one side. It was a 348 copper plated aerotip. This was the old Goex cleanshot or clearshot (never could remember)powder which was real crap.