Ok im confused with the ...

[Kornithium]

Ok how is a gun considered a "stock" gun? Why is there events dedicated to these guns?

I think it means a pump gun thats been converted to run co2, but to be honest, I dont't know.

[rwillia]

No, a stock class marker limits your paintball capacity to a horizontal tube of paintballs (normally ten balls), and can only use 12 gram cartridges. To load the paintballs into the breach, the user must tilt the marker down, or "rock 'n' cock" it. There's more information on CCI's website.

[Skull]

don't get confused though, players often refer to a gun as "stock" if the gun has no aftermarket upgrades... but as far as the a stock class pump marker, ryan has the right idea