Well, they were inaccurate as hell, for one thing. Rifled barrels existed in the sixteenth century, but most flintlocks were smoothbore, meaning the weapon was exceedingly inaccurate outside of very close combat. This is why you could line infantry up in melee formations, tell them to shoot at a similar formation, and they wouldn’t all die after the first volley.
Balancing on the wrist? Search me. There’s a rifle stance where you balance across your elbow, and there are some handgun stances where you use the back of your wrist to stabilize your shooting hand, while gripping a flashlight or knife. But balancing the gun on the wrist sounds really odd to me.
EDIT: It hit me as I was editing in the tags. Balancing across the wrist is a coach gun stance. It lets you keep a couple shells for the shotgun in your hand while firing. It’s a really oddball grip, though, no idea if predates breach loading shotguns. But, if that’s the case, then you’re probably looking at either a blunderbuss, (think of them as the ancestors to the modern shotgun) or a gun that really shouldn’t be there.
With smoothbore firearms, longer barrels equal more accuracy, up to a point. Flintlocks came in a lot of different sizes and shapes, so without having seen it, it could be any number of firearms. On a hunch, I’d recommend checking the blunderbuss as a possible suspect. I don’t think Carbines date back to the Revolutionary War, but it’s possible that their arms master flunked history.
Now, advice on writing in that time? First, don’t call it a rifle. It’s actually pretty easy to mess this one up. Rifles have been around since sometime in the early sixteenth century, but they didn’t become the standardized infantry weapons until the Napoleonic Wars. The practice of calling every longarm a rifle is actually very modern. US forces were still transitioning to rifled muskets during the Civil War, so while I know they had some rifles during the revolutionary war, what you’re actually talking about are muskets.
It’s worth pointing out, at least with flintlock pistols, the reloading procedure was to pour the powder, then the ball, finally drop the cartridge paper in, and tap it all down with the ramrod. This was to keep the bullet in place as the weapon was carried. As I recall, reloading took something like ten to twenty seconds, and was impossible in melee.
Paper cartridges did exist. These were premeasured tubes of paper that would contain enough powder for a single shot, and sometimes a bullet. Most of these were not intended to be simply shoved into the gun, though. They’d be torn open (usually, with the shooter’s teeth) and poured in after the bullet.
Though, there were exceptions, where the entire cartridge would be loaded into the weapon in a single piece. That usually involved paper treated with potassium nitrate. Nitrated paper would burn almost completely. As far as I know, the nitrated paper cartridge came into use with percussion cap firearms, so the 1820s at the earliest.
Anyway, I’m still working through our backlog. Sorry about the wait.