Huron,
In Gooding's "Trade Guns of the Hudson's Bay Co. 1670-1970", there is a short section covering the Imperial line of percussion guns.
He cites that "Shipping records indicate that after 1910, most Imperial muzzle loaders were of 26 bore with 2 1/2 foot barrels although a 1914 shipment included two fo 3 feet and a 1922 shipment (as far as this survey was taken) included 24 inch barrels."
You mention you don't have a "PAL". Not sure what that is?