In the process of developing P90, FN Company gives priority to the development of new ammunition. FN believes that the key to the development of PDW lies in the bullets fired. The initial consideration was to improve the 9mm Parra pistol, but the improvement of 9mm pistol has reached the limit, so we decided to develop a brand-new bullet, which was named SS90.

The development of SS90 bomb is based on the achievements of SS 109 NATO standard bomb developed by FN Company. SS90 bullet adopts a small-caliber slender warhead and a bottleneck shell, with a caliber of 5.7×28 mm, low recoil when shooting, a muzzle velocity of 850m/s, and a larger range and penetration than pistol bullets. Using P90 to launch SS90 bomb, it can penetrate NATO standard thick low-carbon steel plate at a distance of 30m, 48 layers of Kevlar at a distance of150m, and both sides of American helmet at a distance of175m. At the distance of 10 meter, the 24-story Kevlar can resist the ordinary 9mm Parra pistol.

The total length of SS90 bullet is 43.2 mm. Later, FN Company changed the shape of the bullet to shorten its length without changing the casing. The modified bullet is named SS 190, and its length is the same as that of 357 Ma Genan bullet, which is convenient for automatic pistol loading and firing SS 190 bullet. Later, in order to improve the effect of using muffler in P90, subsonic SB 193 muffler bomb was developed.

However, SS 190 is so penetrating that it is not allowed to be sold by the people in the United States. Silencing weapons belong to the category of three weapons. Therefore, FN American Company has specially introduced a new 5.7mm American civilian bomb SS 196SRV-MAX. It is characterized by using a low penetration warhead with a weight of 40 grains.