Yes, a fair amount of shooting was done at 200 and 300 yards in the ACW when the ground was open enough to see one another. (Snipers were using much longer ranges of course.) However, extended firing was generally discouraged at such ranges unless just holding a position awaiting developments/orders, support, etc. since the proximity was not enough to dislodge an opponent for the expenditure of ammunition. With the smoke and men taking cover you could expend a lot of ammo at such ranges. Better to move up to increase effect.

No doubt the Brits had excellent fire discipline, and their navy was especially proficient in that regard.

I also agree about proper assault tactics on positions such as walls and the like. The tactic generally worked where it could be applied and Upton was the key Union practitioner. But trying to form up such columns under fire is going to be a disaster. Artillery would shred it, unless it had cover (woodline), fog, or darkness or some other screen. If anything, it shows how far the fire power had come because you can't march up with superior fire discipline and a moderate advantage and numbers and take it. You have a catch 22: you need several times as much force density to take a position, but amassing this force and planning the attack takes time and good inteligence, and when amassing it one is vulnerable to artillery or flank attack.

The mounted troops used sharps carbines and other breach loading carbines from very early on. Spencer use came later. True there was some reliance on saber early on for cavalry, and some plans for lancers, but soon the cavalry was copying the mounted infantry. They wanted breech loaders that could be loaded in the saddle. The first use of the Sharps by U.S. forces was in 1854. In the ACW there were at least 60 U.S. cavalry regiments equipped with Sharps (more than 50,000 less than 95,000.). Looks like well over 100 cav/mounted infantry regiments using weapons like Burnsides (50,000), Merrill (15,000), Maynards (couple thousand primarily by CSA), Starr (20,000), Ballard (21,000), Cosmopolitan (9,000), Gallager (18,000), Smith (31,000). In essence, the higher tech weapons went to the cavalry. There were also some Colt revolving rifles in service, but they were too long for good mounted use and some times more than one chamber discharged at once (good bye fingers.)

Saw an interesting Feb. 1865 correspondence while perusing the ACW Official Records for Armstrong rifle info last night. It was the Army of Northern Virginia cavalry ordnance chief if I recall. He was trying to get rid of his horse arty's Parrott's/Tredegar rifled cannon in favor of smoothbores, for the reasons we discussed earlier: 1. He didn't need the range for his horse artillery, they rely on moving in rapidly, setting up close and blasting away, then withdrawing quickly if threatened. 2. The smaller rifled shell had less effect and was unreliable (CSA ammo on the reliability.) 3. Shell could not be used to fire over the heads of his own men--because of the lousy quality of CSA fuses and ammunition. This latter part applied to both smoothbore and rifled weapons, but it meant that for the CSA, smoothbores were more practical since rifled weapons lost their main advantage of shell/shrapnel at medium, long range. And of course, by Feb. 1865 the CSA's supply and quality woes were limitless.