If you have some good designs for this group, heck yea! This is one of the few kinds of shows that you know exactly what your audience likes.
How much is a booth going to cost?
Other things to find out is if its a collectors show or not. Collectors will draw a slightly older crowd but if its a generic "gun show", you'll get lots of under 50's which might be more tshirt friendly. Those people will be gearing up for fall hunting so think ducks, geese, deer, camo, retrievers. Maybe get an idea from the cabelas website or gander mountain.