Cannot remove Avenger regulator pin

Hi,

I have a .22 Air Venturi Avenger that seems to have a blown o-ring on the regulator. However, I can't check for sure, as I can't seem to remove the safety pin that holds the regulator in place.

Any suggestions how to remove the pin?

Thanks in advance!
ash
I have removed that same pin before on the 25 cal, All i used was a small punch. It may be a one way pin.