Fabrique Nationale P90 submachine
FN P90 personal defense weapon / submachine gun gun (SMG) was developed in the late 1980s as a personal defense weapon for the troops whose primary activities does not include small arms, such as vehicle and tank crew members, artillery crews etc. Standard pistols and submachine guns chambered for pistol rounds were proved ineffective against enemy soldiers, wearing body armor; Therefore FN designers first developed a new round with enhanced penetration, initially known as SS90. To achieve necessary high penetration while keeping recoil impulse low, FN used a small-bore approach, creating a round that looked much like the scaled down 5,56NATO round.
It must be noted that similar concepts were tried in other countries, most notably in USA, several decades before FN; for example, US Army tested M1 carbines chambered for .221 Johnson Spitfire round back in late 1950s; later on, Colt produced its .22 SCAMP and 5,6x30 MARS ammunition for special SCAMP machine pistol and MARS "mini assault rifle" (a scaled-down M16 rifle) respectively. It must be noted that 5,6x30 MARS round was in a sense a direct predecessor to 5,7x28 FN SS90 round, although the latter featured slightly lighter and faster bullet. By late 1980s a concept of a small-bore, low-impulse "personal defense weapon" (PDW) with good accuracy and lethality at ranges of up to 200-250 meters was well established, although there were no weapons adopted for service yet. FN decided to follow this concept and to create its own PDW using clean sheet approach. Basic ideas used for this development, designated as "Project 9.0", included the following: minimal size and weight of weapon; large magazine capacity; complete ambidexterity; ease of use and maintenance.
