To Saddletank, I am more talking about the changes during the ACW. The main change was that light infantry tactics became considerably more important. Most of the infantry fights became disorganized with regiments breaking into swarms of men; this open order formation prevented them from taking unnecessary casualties.
I mentioned a number of European conflicts because warfare was and is universal. The technological changes that impacted the ACW, also impacted European generals and armies. The point I am making is that
there was no great change at all in infantry tactics with the advent of the rifled musket, or rifled artillery, or even the breech-loading rifle. In the Franco-Prussian War the German breech-loading artillery was extremely potent but this did not affect how the French fought. How could it? It was a new weapon to them and they were bound by their drillbooks to move across the battlefield in the way they had been trained.
It was
exactly the same in the ACW. This idea you have picked up that ACW battles were fought almost exclusively by regiments that had descended into thick skirmish lines is wholly false and I don't know where you have got it from. It did not happen like that. As posters above me have correctly said, units were kept in tight-packed formations for ease of movement and control. Units
were dispersed as skirmishers, (or more correctly, they put out skirmish screens) just as they did in European armies, but the main bulk of the infantry marched and fought in close order, just as European armies did. You only have to read a few first-hand accounts to discover this - letters written home by officers and men - about firefights their regiments were engaged in, to see that ACW troops fought shoulder to shoulder exactly as European soldiers did.
The ACW troops used European drill books and fought using European drill.
The Europeans as you correctly point out, still charged their cavalry en-masse in close formations at the enemy infantry. They had no reason to do otherwise until they learned the effects of modern weapons. There were still cavalry reserves kept in armies in WWI, for use as breakthrough forces should the trenchlines be breached. It was not so much about weapons changing battlefields as the inertia of military tactics NOT changing them.
From a social and cultural point of view ACW armies and generals had a very different approach to cavalry and its tactical use. The battlefields of the ACW were also generally more cluttered with obstacles and made mounted cavalry far less effective. ACW cavalry was used the way it was, primarily, not because of any effect of enemy weapons, but for reasons of different culture and terrain.
But then again cavalry has almost always been stopped by well trained and cohesive infantry. The successful action of the 93rd Highlanders at Balaklava wasn't due to their Enfield muskets, it was due to the hesitation and withdrawal of the Russian cavalry commander. The Russian caavlry withdrew before they got within 100 yards.
If you want to look for one significant difference between European and ACW battles it was the terrain (I would argue a cultural difference too). In the ACW units would pile up fence rails to make impromptu breastworks, even early in the war and some firefights bogged down into groups of men using the best cover they could - but IMHO they only did so
because the cover was there, unlike on European battlefields and
because their officers allowed it which would not be the case for a European firing line (this is the cultural difference I mentioned above). They didn't take cover due to the magical power of the rifled musket, they took cover because it was available.
Its also possible to argue a cultural and societal difference in the minds of the American vs the European soldier where the one had an independent, backwoods, liberal mindset of self-defence in the wilderness while the other carried hundreds of years of tradition and military obedience in his culture.
Once a unit was down in the brush like that, however, as others have said above, it would be almost impossible to get it moving again, unless it was to withdraw. That is not a wise tactical position to be in and was therefore resisted when practical by the officers. This taking cover situation was not universal and of course could not be utilised when a unit was attempting to advance, or otherwise manouver, or else all control would be lost and the attack would grind to a halt.
Such 'thick skirmish line' events were not common and many firefights involved the men standing shoulder to shoulder without wavering.
You need to remember that the vast majority of ACW infantrymen fired far too high and so the potential lethality of the rifled musket was mostly lost on tacticians and observers.
Pickett's division at Gettysburg came at the Union lines in the same way D'Erlon's men attacked Wellington's line at Waterloo.
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Anyway, short answer - you're wrong to set musket ranges out to 200 and 300 yds in the game. The first post in reply to yours is the answer you seek.