Mag classic valve leaks down the barrel. even when with trigger held. HELP

[Jason Reed]

what is wrong with my valve. what o-ring do i need to replace.

[Kevmaster]

you should be able to replace one of the on-off pin orings. if it leaks while the trigger is down, thats prolly the cause

[Jason Reed]

what if it leaks after a long string of shots and when the trigger is not held down.

[toymyster]

Replacing all of the o-rings and seals is probably the best course of action for you!!! That is what I would recommend!!!