pump leak

[C_losjoker]

classic valve automag pump, air it up and it leaks down the barrel. cock the pump and it stops, pull the trigger and it leaks again till I cock it. Do I have the velocity to high, cut the spring to short? if I change the spring to regular size spring, changing it back to semi there is no leak.

wanted to see what you guys thought before I go and try to change a bunch of stuff, or keep running out of air trying to figure it out.

[OPBN]

You need to move down a spacer size.

[captian pinky]

i agree its the spacer size.

[athomas]

I agree the previous posters.

The pump mag works by not allowing the of the bolt to fully reset without manual assistance which is done by the pump. This leaves it slightly forward of its normal position. If the powertube oring can't come far enough forward to press against the back of the bolt stem, residual air left in the chamber will leak out. Install a shorter powertube spacer to allow the powertube oring to move farther forward to seal against the back of the bolt stem.