I should have been more precise and referred to energy. There are varying estimates of how much energy it takes to inflict a wound, from 60ft.lbs in "Hatcher's Notebook", to 80 from another source, to 150 from yet another. Regardless of the figure, 395ft lbs is clearly enough. And to clarify further, obviously not every penetration will result in a fatal wound since placement can vary. Let us say the placement is in an area where a fatal wound could be produced with enough energy. Again, 394ft lbs would be enough if in the right place.
As to the original point which was suitability for defense, this round was specifically developed as a defensive round. This from Wiki:
"The 5.7�28mm projectile potentially poses less risk of collateral damage than conventional pistol bullets, because the projectile design limits overpenetration and has a reduced risk of ricochet.[36][38][39] In the event of a miss, the lightweight projectile also loses much of its kinetic energy after traveling only 400 m (1,310 ft), whereas a conventional pistol bullet such as the 9�19mm retains significant energy beyond 800 m (2,625 ft).[35] This range exceeds the engagement distances expected for the 5.7�28mm cartridge's intended applications, so the cartridge's limited range is not conversely considered a disadvantage."
Important points, I think, relative to the use of the 5.7 as a defensive weapon, either in the pistol or the AR.
Apologies for any confusion. I am not a ballistics expert (but pretty much know where the shot should be placed). I don't feel undergunned at all using the 5.7. I haven't tested it yet, but I am certain I can get off many more accurate rounds in the same time one could with a 9 or a 45. And I would bet good money I can snap them off way faster and accurately out of an AR platform than I can with my 9mm or 223.
More importantly, it's just darn fun to shoot.
