Rate of fire, accuracy, range, and additional bullshit. Most of the limitations on fire arms are due to material science, weight, or just keeping it clean for example a lot of MGs have overheat issues with continuous fire, heavier rifles weigh a lot, and caseless firearms are stupidly complex making them prone to failing due to dirt build up for example.

Mind you this depends on the settings limitations but something as simple as a cooling rune on an MG42 turns into from the huns buzzsaw into the huns sawmill since there would be at minimum reduced risk of barrel slag. You could have single soldiers treating M2 browning like fucking grease guns, weild .50 cal snipers like 1911s, or teleport ammo right into a Heckler & Koch G11 so as to never have to disassemble it to reload.

That's just what I can think of off the top of my head, if the setting allows you could probably create a magitech self charging lasgun from Warhammer 40k, so basically just an archeotech lasgun from 40k.

To quote Speaker D "This is because the metric for OH, FU- is three to six guys with shotguns hanging out somewhere they weren't expecting". This is a quote in relation to World of Darkness by the way.

This whole thing about wands being able to do basically the same as a gun also me realize that one could see the Harry Potter books as a group of kids with stun guns and gadgets fighting the idiot baddies who just use guns and can't get a single plan to go right because of some dumb bs.