Classic valve leaking

[keiko_819]

So I put together a classic mag to give to a friend and the valve leaks out the back, the out the velocity adjustment screw. Any help would be appreciated. Thanks

[blackdeath1k]

Old/bad reg piston? Or old style reg piston in a marker with a level 10?

[Laku]

Or just bad o-ring in the piston?

[snoopay700]

Have you tried backing out the reg?

[Cyco-Dude]

could also be a dirty / bad reg seat.

[athomas]

Is the mag using a level 10 bolt and using the original low pressure level 7 regulator piston? Is the velocity turned up too far? Is the back clean and the piston oring in good shape? These are questions that need to be answered.