Complete noob with BT65 questions

Hello. I bought a Hatsan BT65 off the forums. Two questions. There is a noticeable ping when shooting. I've read about the homemade depingger on another forum. What end of my BT65 tube comes off? How do I bleed the air out of it?

The second thing is I'm shocked how hard it is to cycle the action. Especially the last 3/8 of an inch. I think it might be in part to the annoying auto safety that is at the end of the bolt cycle. I want to be able to have a safety, but disable the auto feature. I plan on pulling it apart and polishing it. Any advice to what to watch out for?