What caliber is 5.7×28mm?
The 5.7×28mm was developed in conjunction with the FN P90 PDW and FN Five-seven pistol in response to NATO requests to replace the 9×19mm Parabellum cartridge.

FN 5.7×28mm
Bullet diameter
5.70 mm (0.224 in)
Land diameter
5.53 mm (0.218 in)
Neck diameter
6.38 mm (0.251 in)
Shoulder diameter
7.95 mm (0.313 in)