This may not appeal to you, nor be appropriate with/for the time constraints on your current trip, BUT......on future trips, if you make the trip out and back an experience in itself, make it PART of your time away (and not an exercise in "just getting there"/boredom, such as what "looking at nothing for 3 hours on the Pike", is to me).........then why not consider taking "the old roads" out and back? We've driven Rtes. 20, 9, 62, 16 etc. either all the way across the state, or as much as possible 'til we ran out of a route number. It's awesome and you see every little town, and what's IN those towns. Rte. 9 west of Worcester is awesome, as is Rte. 20 west of Springfield. You won't need to detour off the Pike to find a gun shop or any other point of interest, you will drive BY the interesting places (or be darn close) just by being on the road you're on. Yes it takes longer so if getting there as fast as you can is a priority, this suggestion is not likely to appeal to you. But not being on the boring Turnpike and instead seeing all manner of cool stuff between here and there, for our family, is priceless. Last year on our way home from the western part of the state we took Rte. 9 instead of the Pike, & we stopped at Quabbin and walked around the hiking trails for a few hours, and also stopped at the museum. We did Quabbin, but we could have stopped any other place that interested us as well. Gun store, local restaurant, whatever. The kids like watching trains and there is plenty of places to see them from "the old roads". The Pike, not so much. This is what works for us but if you're a "as fast as I can get there" via the Turnpike sort of fellow, I understand.
Enjoy your hunt.