Sean: Most guns were designed to serve a military function, and they had the long barrels to act as PIKES, where you put a long bayonet in the barrel, and attack the enemy in rows, on cadence, to the beat of a drummer, and the count of your Sergeant. Because the guns were primarily smoothbore muskets, Accurate fire was not considered at all, but the noise, and fire from a volley of shots into an opposing enemy's ranks might unnerve them long enough to reach them across that 50 yards with your gun now serving as a PIKE. The pike could also be used to repel and kill the horses of mounted soldiers, and cavalry, by pushing the butt of the gun with the instep or ball of the right foot helping to prevent the butt from moving backward, while the left hand held the long barrel with spike bayonet at an angle where a charging horse would impale itself on his bayonet. The row of soldiers behind that front rank were trained to fire over the shoulders of the front rank to hit the horesmen and take them off the horses.
That is the reason for the long barrels on those early guns. They allowed the men to extend the reach of handheld weapons to have an advantage over their enemies. These were very effective tactics when fighting against European trained soldiers, but also came in handy when Indians rush soldiers over open ground.
The short barreled guns worked much better in the dense forests of upstate New York, where there were no roads, or fields, and all travel was done on watercourses. You have to remember that the rivers and lakes there were the interstate highway system of that day. Once you left New York City, and the plains around it, ( White Plaines, New York?) those long barrels became far less useful in combat functions. Indians didn't rush across open fields. They fired at the Rangers from cover, and only charged if they thought they could overwhelm the rangers that way.
The idea that Indians sacrificed warriors to test the guns of soldiers is more Hollywood nonsense. There is no evidence in history to support those ideas. Those warrior were all related, and grew up together. Indians believed in the value of life as much as did any European.
Sorry to get on my horse on this issue, but so much of what most people consider "truth" about history is based on a lot of nonsense that has made its way into films.