The LOCK was the expensive part to make.
To make a long Barrel, all you did was start the weld properly and keep on working.
I have TWO old trade guns, both from the East Coast. One has a 46-inch barrel, the other a 56-inch barrel.
The one with the short barrel is on a 'prentic-made soft-iron Pattern 1853 Lock. The Barrel, also, is definitely 'prentic-made (sloppy filing: no Master would name it, I'm sure): starts as Octagonal at the Breech end, goes to 16 sides, then an elaborate Wedding-band, then Round with a taper to the Muzzle. Very nice half-stock 11-bore, good shooter but needs the Lock tightened up due to soft parts. The long-barrel gun is stocked right to the Muzzle and is on a converted India-pattern flintlock. It is about a 9-bore, paper-thin barrel at the Muzzle, and was used for almost 150 years in birding, whaling and a spot of piracy.
So long barrels were very much the thing. Everyone knew that a long barrel "shot harder" than a short barrel; I have been TOLD THIS by men who shot these guns for a lifetime. AND it was more accurate (proves that a 4-foot sigh radius is more accurate than a 1-foot radius, but let's not disturb anyone). What people BELIEVE is more important than what you can PROVE!
And, yes, the long-barreled guns cost more. The HBC had a definite scale of trade values for guns and it was not SUPPOSED to be a stack of Prime Made Beaver the height of the Muzzle, but my Grandfather (fur-grader/trader at Fort Edmonton) assured me that sometimes a gun WOULD sell for a very high price.
Once the lands were settled and, especially, after breech-loading came in. there were lots of ex-military muzzleloaders available and many of them DID get cut-down, although many did not. I have a French 1852 Musket here which has been chopped, 1855 barrel date, St.-Etienne markings on the Lock. A FOOT has been chopped from the Barrel, 2 feet from the Woodwork. That one is beyond restoration, so it is going to be refurbed as a Sporter, made to look a bit better.
The gun in point is definitely a Trade Gun; no flintlocks had been made for the military for close to 20 years when this one was built. This gun is BUILT LIKE a Bess but a 36-inch barrel is 3 inches shorter than the Indian Pattern, 6 inches shorter than a New Land, 10 inches shorter than a Land Musket. Your Stock has very Bess-like decoration patterns behind the Lock and the whole thing is put together like a Bess, with Pins rather than Bands. The Lock, however, is a more modern shape.
Beautiful old piece! A big bag of TLC, a quart of RLO, a cup of BLO, some very careful work, and she'll be back making noise again!
What a lovely old PRIZE!