I read long ago that the reason for long barrels on colonist-made rifles was mainly because they were forced to make their own powder, which was generally much inferior to European manufactured products. They needed the much longer barrels so that the slower burning powder could accelerate the ball enough to be truly useful. The long rifles were the offspring of Jaeger style rifles that many of the early gunsmiths produced. The smaller calibres developed to save powder and lead, and because generally the game hunted wasn't anywhere as nasty as wild boar; you don't need a .62 to shoot squirrels, turkeys, or deer (with the occaisonal bear thrown in just to keep things interesting). As folks moved West, elk and buffalo were hunted on open plains, so larger calibres were desirous once again, and the guns got shorter for ease of carry on horseback, also, powder had improved and was more available. The military guns were long because in most cases, the troops would only get off a couple of shots before they fixed bayonets (thus turning their long guns into pikes) and charged.
I have heard this before and for sure know of no argument that goes against it. It just makes a ton of sense if you think about going in to the woods for a fortnight or season. A 54 gives you 32 shot to the pound. A hundred shots is three pounds. Where as a twelve bore is twelve shots to the pound, eight pounds to a hundred.
However I look at gun history.
The first rifles were short and about .50 caliber, the gun wasn’t shouldered but held in front like contemporary cross bows. Barrels tended to be in the two foot range.
Many of the early matchlock military pieces were less than three feet.
With the invention of bayonets it made sense to have a long barrel, as tge gun became a spear.
But while this was going on long became very popular for Dutch English and French arms. Not just in country but back in europe. A fine English Fowling piece from 1700 was long. As was a good Dutch gun.
Cr 1740 as riflesmiths began to spread in Pennsylvania the typical gun in New France, Dutch New York, english Virginia was long, and mostly imported from Europe
While it was Germans making the rifles it was English buying them.
I wonder about style.
Chicken egg question, did buyers drive the market for practical reasons or esthetic reasons.
I look at how quick half stocks took over starting about 1810, following english style starting about 1790. Yet full stocks ranged the norm for SMR. Even long after they virtually disappeared in the rest of the country.
Makes me wonder.
I am put in mind of French trade guns. To compete with the French market the English consciencly imitated it, then later when Americans and Belgian makers were supplying NWG they directly copied the English trade guns. Even the sea serpent side plate ( dragon) started as a mark of sea guns for civilian ships on Dutch vessels, but this became the mark of trade guns, and fell out of use on civilian guns.