The Bizon PP-19 SD is a submachine gun found only in helicopter crash sites. It has a large magazine containing 64 rounds, but they can be found only in helicopter crash sites, making them very rare.
This weapon is often used as a throwaway weapon due to the rare magazines and high rate of fire, making it useful for only as long as the ammunition found with it lasts.
The Bizon PP-19 SD is silent, with its sound resembling the M4A1 CCO SD's sound, but its iron sight makes aiming much more difficult compared to the M4A1 CCO SD. It also has a very bright muzzle flash, similar to unsilenced weapons, giving away the shooter's position at night. This disadvantage is counteracted by the surprisingly low recoil, allowing you to take more shots before having to compensate. That low recoil is very useful, because the low damage of the Bizon means it takes a lot of bullets to kill a target, barring any headshots.