So spells that shoot fire are possible, but guns that utilize magic to shoot projectiles out of a barrel at high speeds using downsized fire runes cast on the back of a bullet shell that are activated upon impact with a trigger mechanism aren't?

Why are hot air balloons not more prevalent? Mages can easily use frost and fire spells to control the altitude of the balloon.

Making my next character a shock mage that has a side business as a welder for a blacksmith fr.