Has anyone seen/fired one of these?
With the penetration stats they list at the FN site, it seems to me like it would overpenetrate nearly always. Of course they won't let me have one anyway. (lE only)

Velocity is nowhere near that of the 5.56 x 45 round and with a lighter bullet, fragmentation is iffy.  The bullet would tumble as this is dependent on the length.  I doubt overpenetration would be an issue.  Close-range lethality would be.   Dr. Fackler wrote a scathing letter to the editor in American Rifleman shortly after they ran an article on it claiming to have a wounding profile similar to an A1.

The bullet is designed to penetrate, but it is very unstable due to bullet core(steel,aluminum).  The bullet will destabilize and tumble upon contact causing a rather shallow wound channel; I believe it's about six inches in ballistic gelatin.

Fabrique Nationale P90 and Five-seveN Ammunition
SS190
The SS190 is the 5.7x28 mm Ball round. Its projectile will perforate any individual protection on today's battlefield including the PASGT kevlar helmet, 48 layers of kevlar body armor and the CRISAT target (titanium and kevlar). The SS190's conventional design allows it to be manufactured on existing production lines, and its lead-free composition eliminates range contamination.

Caliber 5.7x28mm
Cartridge length 1.6 in. (40.5mm)
Projectile weight ˜ 2.02g
Recoil implulse ˜ 1.95 kg m/s
Chamber pressure 345 MPa
Muzzle velocity 715 m/s
Perforation at 200 m - Body armor (48 layers of kevlar)
- PASGT helmet


Sb193 (subsonic round)
The Sb193 cartridge has been designed to deliver a muzzle velocity of about 300 meters per second. This eliminates the loud crack caused by a bullet travelling faster than the speed sound. To enable the weapon to function reliably when firing this ammunition, the reduced velocity is compensated for by using a heavier bullet. The subsonic round is identified by the bullet's white tip.

Cartridge length 1.6 in. (40.5mm)
Projectile weight ˜ 3.6g
Recoil implulse ˜ 1.3 kg m/s
Chamber pressure 345 MPa
Muzzle velocity 300 m/s
Energy loss a 50 m ˜ 100 J
Effective range (penetration
of 24 layers of kevlar) 50 m

so, this round will penetrate a kevlar helmet out to 240 meters, yet only go 6" in tissue? How do they accomplish that?
I'm obviously no ballistics expert, but that doesn't seem possible.
Thanks
AIRBORNE

Me want! Me want!

I have fired them, it duplicates a 22mag.