Britney spearz, OOPS you did it again

(couldnt resist)
the pump has to be threaded in the butt of the gun all the way, and when you pump, push all the way through gently, you should feel pumping take place and yes there will be resistance as you do this...
if youre still uncomfortable, maybe take it back to the store and have them pump it for you so you know how its done...
take care Britney