Isnt that a military weapon?
And isnt it british? As far as i know this is situated in North America.
And i recall seeing british troops also using the mp5 sub-machine gun.
Something to point out about the p90:
The P90 is the ultimate system for operating in urban and other close-quarter battle scenarios. This system is built around our revolutionary 5.7 x 28mm ammunition, which gives you the best of both worlds: It easily penetrates soft body armor, but since the dual-core projectile destabilizes on impact, overpenetration is unlikely. The P90 provides a compact, lightweight and completely ambidextrous platform for this ammunition. The 50 round magazine runs horizontally across the top of the P90, keeping it compact and empty casings are ejected downward, where they cannot interfere with the user. The P90 fires from a closed bolt, giving it outstanding accuracy and making it easy to keep on target. The Five-seveN tactical pistol, also chambered for 5.7 x 28mm, is an excellent companion to the P90. The FN P90 sub-machine gun is the ideal personal defense weapon for armored vehicles or helicopter crews. Perfectly fitted for law enforcement tactical teams.
With a speed of 500-700ms at the end of the muzzle it isnt a humain weapon, especialy since its able to penetrate most armors.
So if we want realism, this is a extremely deadly weapon. And, are we going to work with iron sights?