Mine had a very small leak develop at the fill nipple. Pitbull airguns says 90% of the time when they leaks it is there! "Possible cause is dirty, moist air"Soapy water probably works best to find the leak. I got lucky finding my leak, using silicon spray to get lube inside the gun I sprayed the fill port before connecting my scuba tank... and saw bubbles at the threads! Since I already have a Captain O-ring rebuild kit, just replaced the O-ring going into the receiver under the fill port adapter, cleaned and changed Teflon tape on the fill port and air gauge. It has been holding 3,200psi for months, no more leaks.For reference it was about a year before that bulldog developed a leak, and it was only filled from a scuba tank fed by a Yong Heng with two inline filters.(DEGAS BEFORE REMOVING ANYTHING UNDER PRESSURE)
That screw goes into the side of the hammer, through the slot in the receiver. Apply a little blue loc-tite on the threads and that will stop it from coming back loose. I applied blue loctite to my hammer tension screw so my settings never move...
Cant post a link. Search Youtube Pitbull airguns has a new teardown and reassembly of a new Bulldog...Title of the video is: "COMPLETE Benjamin Bulldog Teardown & Reassembly"