The 9×39 mm is a Soviet / Russian rifle cartridge. It is based on the Russian 7.62x39mm round, but with an enlarged neck to accommodate a 9 mm bullet. The cartridge was designed by N. Zabelin, L. Dvoryaninova and Y. Frolov of the TsNIITochMash in the 1980s. The intent was to create a subsonic cartridge for suppressed firearms for special forces units that had more power, range and penetration than handgun cartridges. The 5.45x39mm cartridge introduced in 1974 for AK-74 lacks bullet weight for acceptable energy at subsonic velocities. The bullet of the 9×39 mm is approximately 16 g (250 gr), double that of the 7.62×39 mm, and is subsonic. This slow velocity does not produce a sonic boom, but does limit the effective range of a weapon when compared to non-suppressed assault rifles. The round has an effective lethal range of 300 to 400 meters and a maximum penetration of up to 10 mm of steel. Like the 5.45×39mm cartridge, 9×39mm SP-5 features an airpocket in the tip, which vastly improves its capability to yaw; with such a long projectile, yawing can be quite violent.
SP-5 (7N8) - The SP-5 (СП-5) (SP: Spetsialnyj Patron; "Special Cartridge") was developed by Nikolai Zabelin. It is a conventional lead core FMJ bullet, but developed for accuracy.
SP-5UZ - The SP-5UZ (СП5-УЗ) is an SP-5 variant with an increased charge intended for a factory-specific strength testing of the weapons.
SP-6 (7N9) - The SP-6 (СП-6) was developed by Yuri Frolov. It has a hardened metal armor piercing core. It can penetrate 2 mm (0.079 in) of steel at 500 meters or 6 mm (0.24 in)of steel, 2.8 mm (0.11 in) of titanium or 30 layers of Kevlar at 200 meters. At 100 meters it penetrates 8 mm (0.31 in) of steel, while retaining enough power to neutralize a soft target behind it.
SP-6UCh - The SP-6UCh (СП-6УЧ) is an SP-6 variant intended for training.
PAB-9 (7N12) - The SP-6's bullet is expensive, so an attempt was made to make a lower-cost version of the cartridge. The PAB-9 (ПАБ-9) used a stamped rather than machined steel core. It sacrificed too much performance to be usable. As of 2011[update], its usage is prohibited.
SPP - The SPP (СПП) (SPP: Snaiperskie Povishennaya Probivaemost; "Sniper - Increased Penetration") is a sniper round with an increased penetration.
BP - The BP (БП) (BP: Broneboin'ie Pulya; "Armor-Piercing Bullet") is an armor-piercing round.