.500 - I made the statement only on the appearance of the two. The .577 having an ogive as-in the typical .577 Kynock-type bullet, whereas all the .600's I've seen are round-ball-ish in shape. I have also read years ago, the .577 well outpenetrated the .600, however the bluff nosed .600 did smack harder due to it's shape with slightly larger diameter. Perhaps that has changed in more modern times? To an elephant I suspect the difference in bore size or the difference in section density means little whereas construction is the important factor.

If both are more than necessary with most any ammo, this is all merely conversation and nit-picking.