Goto Ammo Mart, I bought 40 clips of Uzi Ammo.. 5$ each, and 50 clips of HG Ammo, 4$ each.
P.S. P-90 should load 50 bullets, not 15 O.o
Caliber: 5.7x28mm SS190
Weight: 2.54 kg empty; 3 kg loaded with magazine with 50 rounds
Lenght: 500 mm
Barrel lenght: 263 mm
Rate of fire: 900 rounds per minute
Magazine capacity: 50 rounds
Effective range: 200 meters
Source:
http://world.guns.ru/smg/smg13-e.htm