FN Herstal P90
5.7x28mm
Introduced in 1990, the P90 was an attempt to move away from 9x19mm in a Personal Defense Weapon in conjunction with the Five seveN pistol.
However it was adopted by many military and special police forces and is currently in service with these forces in over 40 countries.
It is a bullpup design with several innovations like ambidextrous controls, a top-mounted magazine, shell ejection through the bottom and the very small 5.7 ammunition which allows it to have a 50 round magazine.