Antique weapons, such as muskets and crossbows, are very slow to reload. Each weapon tells you how many actions it requires to reload, such as 1/3, which means the weapon can fire every third round if the firer does nothing but load every action. Characters can load and walk at no penalty. If the character tries to run and load, he must make an Agility roll (at the usual -2 penalty for running). Failure simply means no progress toward reloading was made that action.

Savage Worlds Deluxe Edition p. 55