It really all depends on the girl...
I don't think I would make it priority topic #1. But if you go out a few times, it's bound to come up in conversation at some point. If she's already to the point where she's at your house and you're getting cozy and she notices the big green cabinet... chances are she's in to you enough that (at least for that night) it won't matter. I'll be honest, the hobby could be a make-it-or-break-it thing, but if your new date really likes you, she'll accept is as part of you. You never know, you might find yourself with a new range buddy.
One way you could bring it up is, "Oh I'd love to go to the zoo with you on Saturday, but I've already made plans to go shooting with some buddies of mine. You're welcome to come along if you want." (and actually genuinely mean she's welcome to tag along).
But then again, the last time I tried dating, I told the guy I couldn't live with a smoker. He stopped smoking that night, and moved in the next week. Seven and a half years later, I still haven't been able to get rid of him.
