SIG Sauer P320 CO2 Black.177 Cal, 4.5mm CO2 Pellet Air Pistol by Sharda gun house The SIG Sauer P320 CO2 Black is now available.A revolutionary weapon in the field of CO2 air pistols is the 177 Cal, 4.5mm Pellet Air Pistol. This 30-shot repeater, which was unveiled at SHOT Show 2017, is evidence of SIG Sauer's commitment to pushing the envelope. As the first belt-fed semi-automatic pistol with a 30-round capacity, the P320 is notable for its robust metal slide and polymer frame construction. As it fires, feel a realistic backlash.depending on the weight and composition of the pellets, 177 pellets at up to 380 fps. Hours of enjoyable shooting are guaranteed by the 12-gram CO2 cartridge that is covertly stored in the grip.