The cost of opening any business is determined by a detailed business plan. Write one, which requires research about rent, space, build-up, advertising, inventory, etc.
the average cost to open a gun shop can very. It widely depends upon how many guns you will have in your initial inventory, as well as personel needed to run the shop. Another key aspect is the amount of money needed to rent or buy a store front. Add all those up and you will know.
The average start-up cost for any business will depend on the size business you plan to have, the prices of inventory, and the cost of real estate in your area.
Cost of obtaining the license, cost of premises, staff and inventory that is not provided on consignment. Insurance and utility costs. Making the store secure against break ins and installing the alarms.