Sig Sauer P365 BB, CO2 Pistol, BB, 3.1 Barrel, Plastic, 280 Feet Per Second, Black, 20 Rounds AIR-P365-BB The P365 redefined the micro-compact pistol category with its unprecedented capacity and shootability, quickly becoming the number-one-selling pistol in America. Now, you can get the same game-changing pistol in the form of a 4.5mm CO2 airgun. Whether you are looking for a low-cost alternative to dry-fire training or simply want a micro-compact airgun for some backyard plinking, the Proforce P365 has you covered.