i have had this gun for a year now and was totally satisfied with its performance when suddenly its velocity dropped from 900 to 450 feet per second at the muzzle. I decided to change the regulator and installed a new Huma imported from Airguns of Arizona USA. with new regulator and all O rings replaced the velocity is not picking up and stays around 500. I noticed while disassembly that its hammer was sticking in its receiver and I therefore polished and cleaned it till it started to move freely in its way. i also replaced the hammer spring with a more rigid one but to no avail. am at my wits' end as I dont know what to do next.......any help is appreciated