BigNate said:
I always understood that the intent was a lightweight, low recoil pistol cartridge that could defeat soft body armor - with the last thing (pistol cartridge that can defeat soft body armor) being the real selling point for a lot of folks.
The problem is that the ammo designed for it that actually defeats body armor is forbidden to be sold to you and me. Although it is not supposed to be available, occasionally small EXPENSIVE batches hit the internet and can be had.
https://ammosupplyusa.com/product/federal-fnh-5-7x28mm-ammunition-ss198lf-27-grain-green-tip-hollow-point-brick-of-500-rounds/
FN 198LF.jpg
Otherwise, with any other loading, all you're doing is slinging .22mag type performance. It's a great round for handgun hunting rabbits out to 150 yards,...if you can shoot that well. While having a 5.7 handgun is better than having no handgun, and while it might maybe be better than .32acp or possibly even .380acp under certain circumstances,...the only real advantages are that they tend to have 20+ round magazines, don't recoil much and will deafen your opponent (along with yourself).
They might be a neat range toy, but I'd never knowingly carry one into harm's way.