I would advise you to just be yourself. Period. If who you are is really completely about guns and collecting....and little else.... fine. Tell her up front. I doubt that this is the case. You are probably much more complex than that....just like everyone else. Your hobbies are not, I repeat, not, critical information. Critical information for women includes employment, past marriages, STD's, children, a very rough idea of your financial condition and a glimpse of what your dreams of the future might be.
If your fascination with guns is just a part of who you are, as it probably is, I might advise you to just let it ride for the first several or more dates. Your investment in a few dates is little and, by now, you should be man enough to handle a bit of rejection.....for any reason....if it needs to happen. And if that happens, you are not "wasting your time", but practicing towards perfection.
After you are acquainted, either she digs you or she does not. If she does not, simply give it up. If she does, then and only then will you have a feel for if it is worthwhile proceeding into the more intimate and personal territories.
I was single (and very, very much in the game) until age 45. (So I am not one of these guys that married his high school honey at age 19 and claims expertise in a field that he does not in fact have.) I never disclosed everything or even close to that at the beginning. And you shouldn't either. That is simply bad practice to say nothing of rather poor strategy. Developing a relationship is all about discovery. And you have to make her want to discover more. And dribble it out in measured doses, but always remain genuine. I am not advocating secrecy, but "honesty" is not about spilling your guts and telling all. It is about being who you are and being true to your core self.
Our society has a considerable amount of gun-bias. An unfortunate fact, but a fact nonetheless. You can't afford to lower your odds by getting into any significant revelations of your politics or other controversial personal matters early on in any relationship. Prejudice is simply too prevalent. But once we know someone, our prejudices, unless very strongly held, become much less significant in our assessment of others. Dating and mating is all about manipulating the odds and keeping the volume of contact and repeat contact maximized. You can't afford to turn anyone off from the get-go, so stay away from the controversial stuff for starters. Frankly, in thirty years of dating, I had only one woman really freak out when she saw a .22 rifle in closet. I wasn't like I had a Glock in my pants or anything. But I managed to prevail in spite of that even with her, believe it or not.
My wife of fifteen years, when we met, was quite the tree-hugger, the wolf lover and even somewhat anti-gun, but not rabidly so. If she had been, I would have dumped her. But hey, she dug me for who I was and for what I was....as a person and as a man and as a good prospect husband. The content of my character, or so I would like to think. That's really the bottom line to all this, man.
I bought her a S & W revolver as a wedding present. She now packs regularly. If I can do it, so can you. And hey, maybe the wolves are worth saving.