David Zietlow wrote:Speculation: a firearm of mythril-bashing caliber would probably have to be a two-hander. Give it a bayonet, and maybe even a hook--you could fashion a polearm out of it, adding close-range options to armored combat. Using it for melee may damage the firing mechanics (that's part of the game). Mythril's strong enough that bashing would do little good, but maybe you can thrust between what little gaps the Maximilian-esque armor has, or fire point-blank for increased lethality...I'm just rambling off the top of my head, but this might work.
There's a great deal that you could extrapolate from similar situations that realistically happened in history. One of the things that comes to mind is the introduction of the tank in World War I. Early tank armour was necessarily quite thin since the engines available could not propel a much heavier vehicle to a reasonable turn of speed. As a result, the Germans experimented with special kinds of rifle rounds (among them ones where the projective was reversed so that it struck with the blunt end first) that proved capable of penetrating tank armour at long range. Pretty much all sides also began to develop anti-tank rifles of a size and power comparable to modern anti-materiel rifles; I suspect that similar weapons would have been an important development priority in a Civil War milieu with armour that could resist ordinary musket balls. Perhaps they would have taken a form similar to early wall guns (search for the German term "Doppelhaken" or Eastern jingals, probably crewed by two soldiers rather than one. The impact of the large bullets from such a weapon would have been equivalent to (at least) a strong blow from a stout warhammer and they would have allowed properly-equipped teams to engage armoured troops from a much longer range, than, say, an extra-heavy revolver firing the equivalent of shotgun slugs (Le Mat, anyone?)
And of course there's still rifled gunpowder artillery. No matter how strong an armour is, a single solid bolt from even a small gun would probably have been able to put a hole through several knights in a row--or crush them to their deaths even if the armour managed to stay in one piece.
Another path of development that would be of some interest is naval history. In the 1860s, improved steel production methods scaled up better for armour than for guns. While bulletproof armour for the individual soldier or horse was still too heavy to be practical, large thick slabs of steel armour for ships proved much easier to manufacture than large guns that could penetrate such armour. The reason is quite simple: steel slabs for armour were just that--slabs--and even contoured pieces didn't need anything like the detailed shaping that would have been essential for personal body armour. On the other hand, extremely large muzzle-loading guns were very impractical to operate; some nations did experiment with such guns (especially the Italians with their 16-inch guns), but their reloading procedure was so difficult and complicated that there was little prospect of realistically loading and firing a second shot once battle was joined. Breech-loading guns didn't even count since the obturating mechanisms that would make them practical (de Bange interrupted screw breeches, Krupp sliding wedge breeches, brass or steel quick-firing shell casing large enough for artillery) had not yet been developed. As a result, the two major ironclad battles of the era (Hampton Roads/Monitor vs. Virginia and Vis/Lissa) featured a large amount of ramming, and this led naval tacticians throughout the late 19th century to put too much emphasis on ramming even when gun technology had caught up and allowed battleships to engage each other at longer ranges than ever before--a misconception finally broken at the Battle of Tsushima. So yeah. If you want a 100% historically correct predominance of heavy armour, think of ships within this narrow window of time (1850s/1860s to 1870s or at most early 1880s).
If none of those things are like what you're looking for, I'll just bring the discussion back to the issue I mentioned early on: you don't need armour to have lots and lots of swordplay in the mid-19th century. Champions challenging each other to single combat between the lines wasn't unheard of either; cavalrymen (especially dashing light cavalrymen like hussars and chevaulegers) did this all the time during the Napoleonic wars and the romanticism of that time still had a strong grasp upon the mind of the Civil War officer.
What I like about swords is that its art is complex, intricate, subtle--a deep game, far more than gun warfare. The samurais must have been devastated when any peasant could pick up a gun and render worthless their lifetime of training. (It's a shame Hollywood wastes its intricacies though--there's so much untapped potential in it. One of my all-time favorite movie fights is the climactic duel in Troy--you can feel the strategy behind it, the depth of the game. Too often I'll be caught in the illusion of a movie until the fight scenes, but that Troy scene's believability did wonders for the drama, the intensity of the scene for me. That's so much more than "cool factor.")
Maybe you should consider a different dimension to the complexity and intricacy of war. Firearms didn't really make war simpler and more brutal as such; while gunpowder warfare may have required less skill in individual handling of arms, gunpowder armies actually required
more training than earlier ones since the characteristics of their weapons as well as the larger numbers of soldiers involved meant that teamwork had become more important than ever. If your character was a low-ranking officer, why not show her skill in leadership and tactics? Go read Bernard Cornwell's
Sharpe series if you need to convince yourself that such things could work. Sharpe
does get into a large number of swordfights throughout his fictional career, mind you.