Well, As promised, I did review the reports on this remarkeable handgun/cartridge combination.
It offers concealability, low recoil, hi penetration through body armor of most types, a handsome and well backed wepaon.
I puts me slightly in mind of the 5.7mm "Vixen"catrdridge developed for the M-1 Carbine, not up to 5.56 Nato performance, but, for most applications, clearly superior to the Standard M-1 Carbine round IN THAT WEAPON!!!!! (barrel change only required.)
The site I found gave little atual performance information, But I a guess:
the impact at close to moderate range of a 40-45gr bullet, moving at least 1700 fps would be fearsome. "Knockdown", the elusive intangible would remain the only question unanswered..
If they have kept the stabiization on the "edge" it would allow instant "tumbling on impact" and disitergtration of the projectile, but, though such an impact/wound would be devastating, s 'barely" stabilzed bullet might not deliver the desired penetration.
Nonetheless, In the words of the great Will Smith: "I have GOT to get me one of these!!"
Sorry for the delay.
"All Enlightenment Gratefully Accepted"