[(E)]

Match locks and wheel locks may be inconvenient/expensive enough for a version of the create fire/ignite fire spell to take their place in early firearms. If this does happen there may not be the impetus required to develop flint locks.

Other simple spells might remove the need to clean out black powder residue. This may decrease reload time. It may also (arguably) remove some of the reason to progress past black powder.

Conceivably this could make something like the whitworth rifle (hexagonal bullets, very accurate, but prone to fouling) represent the pinnacle of mage-lock firearms. Spells to do with measurement could also increase the accuracy of early firearms, both directly as enchantments on a weapon and as engineering tools.

Having even cheap enchantments required to manufacture a firearm makes for some interesting ramifications.

[Edit] Air rifles might also be greatly improved with a few simple spells.

Early cannons would benefit from a utility mage.