Interesting that pistols could be loaded while muzzleloaders can't.
Here, no modern firearm can have a loaded magazine installed, and of course, nothing in the chamber. Here, if a cap and ball revolver or muzzleloading pistol is in the vehicle, it had better be encased, locked, unloaded, no powder, no balls, no prime. Some might go so far as to state it also must have a trigger lock on it.
At one time here, it was legal according to the BC game laws to have a charge and ball or bullet loaded as long as the gun was unprimed, however the Federal law stated that that was a loaded gun and illegal. It took a couple years (of coure cases) to straighten that out to being unloaded by both governing laws.