What's a muzzle loader? How just cracking it open like a breech loader. In a world where hand crossbow welding dragons who says the tech has to mirror our history. One my friend came up with that idea back in 3E to try to fit # of attacks per round with a high level fighter.
I would do hand cross bow = pistol 1d6 damage. OR 2d4 damage and just increase the range for each type.
30/120 pistol 60/180 rifle 90/360 hunting/sniper rifle.