here is the DIRECT EXERPT from the PGC regulation book:
Loaded Firearms - Vehicles: A firearm is considered loaded when there is live ammunition in either the chamber or attached magazine.
It is unlawful to 1) have a loaded firearm in, on or against any motor vehicle, regardless of whether the vehicle is moving or stationary; and
2) have a loaded firearm in watercraft under power, or shoot from a powered watercraft until the motor has been shut off and the craft has come to a complete stop. Holders of License to Carry Firearms permit are exempt, but keep in mind that most sporting firearms are not authorized
by the permit.
It is prohibited to have any muzzleloading firearm that has a live charge of ammunition in its firing chamber and a primer, flash powder or a battery, whichever is applicable, properly positioned in the firing mechanism of the firearm rendering it capable of discharge, in, on or against any conveyance propelled by mechanical power. Any
crossbow that has been cocked and has a bolt affixed onto the string or positioned into the firing mechanism of the device is prohibited in, on or against any conveyance propelled by mechanical power. For complete safety, a muzzleloader and crossbow bolt should be fired into soft ground before those devices are transported in a vehicle.