Walther CP99 Compact is a CO2 replica of Walther P99 compact modification. As a source of power 12g CO2 cartridges are used. It is a semi-automatic BB Repeater (.177 steel BB are used). The velocity of this gun is 345 fps. CP99 Compact has a blowback action. That is why it feels more realistic than its brother, CP 99. But CP99 is a pellet pistol with a rifled barrel, while the CP99 Compact is a smoothbore BB gun. That is why CP 99 is more suitable for target shooting (it is more accurate) and CP99 Compact is great for fun or plinking.