SIG Sauer P226 CO2 Semi Auto Air Pistol .177 Caliber 16 Rounds Metal Frame and Slide Black AIR-226F-177-12G-16-BLK. The SIG Sauer P226 air pistol uses a 12-gram CO2 cartridge. It features a semi-auto blowback design, a 16 round mag, manual safety, and fixed sights.