We're very much aware that the gun sway in-game is higher than in "real life". This is due to a mixture of both game mechanics and trying to simulate the nerves and fear of a horrible death the soldiers faced on the field. We have many historical rifles/muskets from the civil war (some where even used in the war) in the office. Besides that, we were on shooting ranges, testing the performence of the weapons with real ammunition.
The majority of weapons of the Civil War were more accurate than the most used during the napolenoics due to rifling/minie balls used. From a gameplay perspective, lowering the gun sway amount when aiming to a degree would result in far less lines being able to form and fight. The only other solution to this than a simulated combat environment aiming solution is to downright make the weapons less accurate (which I imagine would make a lot of people upset also). Besides that, unlike similar games, we have realistic bullet ballistic, which would make the line combat even harder, if there wouldn't be gun sway