RB Fuel Gun
If your fuel gun is leaking - check the "o" ring. Clean the gun after each days use - I put "TrFlow" on the oil rings - it swells them slightly and the "gun" doesn't leak. Be sure the gun is adjusted properly - the O ring should seat firmly in the barrel.
With The RB and other guns of that design - keeping them clean and the "o"rings mantained is critical. (If you haven't cleaned your fuel gun - take it apart look inside the "junk inside" will scare you)