Jammer Six -
Yeah, I'm a boss too. Hobbies aren't religion or politics, and it's quite common for work groups (where I work) to chat about hobbies. But supervisors generally don't fraternize with their crews after work.
Do you and your boss have a relationship that can handle things going wrong outside the workplace? While a disagreement with a coworker over a common interest might be somewhat troubling when you still have to work together, that same disagreement with a boss might be untenable.
Unless you guys are family, I wouldn't act as his reloading mentor...