BB Gun Help.

[Oreo]

Just a quick question, im interested in buying a new M47A2 Airsoft Shotgun and it says it fires at just over 300 Feet Per Second, With 0.12G Bb Pellets, can you guess what Power Joule rating this is, and if so would it be ove thee pwoer of my Walther P99 0.5J Pistol, Thanks.

Heres the Gun > Airsoft BB Shotgun A2 Riot Shotgun only £22.99

Thanks Again.