Do you have to buy a new gun for each city or can you just keep upgrading?

Need to buy a new one

I like this question. I used 1 rifle “Dragon” for a very long time, because it was 1-3 tier weapon. I upgraded it 100% beyond the amount shown on the rifle stat chart. As long as the weapon stats meet the levels criteria you don’t have to buy a new one. Save your money for the big dog “tier 21”