Watched an interesting video by a guy named Paul Harrel (sp?) where he chronographed 10mm 180 grain jacketed hollow points and 185 grain .45acp jacketed hollow points head to head with same barrel lengths. With three different ammo choices, the average difference in velocity was between 100 and 200 fps with the edge going to the 10mm. But, keep in mind the .45acp was 5 grains heavier - with translates to a fraction more mass delivered on target.
His methodology wasn't that scientific, but it led me to consider the 185 grain jacketed hollow point in .45acp is no slouch as a defensive round
The trade off, though, is penetration. Likely that lighter, faster, .45 ACP is going to be expanding to a larger size and penetrating a good bit less.
