In my experience, the main problem is the hole in the threads has to be perfectly on the bottom to line up with the hole in the ASA. I made a mark whre they lined up, and when I tightened it up so it was tight, the hole in the threads was about 10 degrees past bottom. No air getting in the body.
Also check that the hole in the bottom of the bolt is lining up witht the air passage hol ein the bottom when the sled is in the forward/firing position.
I don town PbPumpShop.com anymore ! Please contact the owner thru the website.
Al I have left for sale PB related is pump related headbands and tshirts.