Odds of Hanging On
If you don't break any laws, you're already halfway there. The other half is what every business owner has to deal with: the whims of the market.
Keep your business relevant, stay ahead of the competition, don't carry more stock than you can sell, and make sure your customers continue to do their business in your shop. People may support your right to sell firearms, but that doesn't mean they'll keep you in business if you overcharge them.