on/off problems

[ClassicMagAuto]

I set up a KAPP drop with an on/off on my mag i got from a freind... but when i screw in the on/
off knob it starts to leak like crazy... Am i doing something wrong? or what?... sorry i'm a noob to the whole drop thing, but hey everyones gotta start somewhere

Thanks ,
Coray

[Chronobreak]

is there an o-ring inside teh on/off on the pin? ifnot there should be replace it if needbe or sue some teflon on the screw in aprt