Polymer One-Shot Cannon

Polymer One-Shot Cannon is heavy firepower in a disposable package! This plastic blaster from Kang Tao is the ultimate last-chance weapon- after all, you're not going to need more than one explosive 13mm bullet to get the toughest pursuer off your tail! To keep costs down, the "OneCannon" is made from inexpensive materials, and the shell is filled with stable explosive materials.

Notes: The 13mm shell is a low-velocity HEP (High-Explosive Plastique, cratering) round which does 406+2: damage is 1/2 real, 1/2 stun only- armor has no effect and is damaged 2 levels. The gun is so poorly made that if it jams, it breaks- and there's a 10% chance the weapon explodes, doing 206 to the firer's arm!

Source

 * Chromebook Volume 2, pg.36
 * Blackhand's Street Weapons, pg.32