[Maksimum_Fire]

Power upgrades at the blacksmith not affecting guns has been an issue for a long time, without much of a good reason.  This affects all kinds of guns- shotguns, snipers, handguns, special firearms like the Jackhammer, and with no regard to multishot or singleshot.  Guns just don't get power upgrades, even if they're mutated.  Weapons mutated into guns do get power upgrades, however.

Notable about this is that you CAN pay for power upgrades at the blacksmith, it just won't do anything.  This is an easy pitfall for new players especially to fall into and should be dealt with sooner, rather than later- either by making upgrade power apply to guns properly, or by replacing the Power upgrade for guns with some other UL boosting attribute.

To test:  Upgrade a gun's power stat.  Its supposed power stat will be listed in the weapon description, but the actual power that it uses for attacks and skills will be displayed next to it in your inventory.  Nitrogen Drop, based solely on weapon power, can also easily demonstrate this issue, as there will be no change in damage after upgrading a gun's power.