I might as well post my observations and studies. First the account of Morgan's Riflemen at Saratoga is often used by arm chair quarter backs to support their theories on why the rifle should have been used more. If you read the "rest of the story" the British unit that they ambushed lured them into a group of regulars (some say Grenediers) that tore them to doll rags when they pursued the retreating British. It would not be too much of a leap of logic to think that that might have inspired Morgan's tactics against Tarlton at Cowpens. That rifle unit was not mentioned after that encounter. GG Grand dad was not stupid and the tactics used were the best for the technology of the times. The American rifle units did not have a standardized weapon, they were sporting arms and not military arms and were too fussy. Look at the care we use to keep a flintlock rifle shooting in a match today. When I had a repo Bess, the thing was about as fussy as a percussion. I used it to shoot a few rounds of trap at shoots before I built a 12 bore that fit me. The British employed the most successful rifle units for the times in the Napoleanic wars and they utilized disciplined hand picked soldiers (ones that could shoot) and issued the Baker rifle, a standard caliber short barreled rifle that looked little like our long rifle. The first American military rifle, the Harpers Ferry or its evolution's) is more like the Baker than a long rifle. I will point out that when the British held off the 4000 Zulu at Rourkes drift they had rifles. One source claime dthe empty cartridge count was close to 20,000 rounds they did not eradicate all 4000 Zulu's. Some of this might have been had they had rifles may not be as true in fact as some speculate.
Shotguns have been used in Iraq by the Marines in urban warfare, the American introduced model 97 pumps in WW1 to clear trenches, mountain men used them for night watch and modern and frontier lawmwne carried them to keep the piece. It is said Wyatt Earp supplemented his income with a double barrel he used to collect a few buffalo hides with. The NWTG was the primary trade item in the Great Lakes as it was affordable to the natives, rifles were more spendy. The NWTG lasted as a trade item until the breech loader got popular. Trade rifles were not really a practical item until the 1820's when the idustrial revolution permitted faster and less expensive production. they were available to Natives and whites alike.
Most hunters in my area admit that if they only had one gun it would be 12 ga repeater. With a shotgun, whether muzzle laoder or modern one can hunt ducks, grouse and other small game, and nail a few varmits as well as use a solid ball for deer. People get deer every year with them. I had an uncle that hunted squirrrels, ducks and quail as well as deer with an old single shot 16 ga. Put him back in history and a fowler would have worked as well.
Both rifles and smoothbores have their use, and a rifle is not worth a darn for my uses with a smoothbore. If the shots are longer I really do not care for a smoothbore either.
DP