For the Napoleanic Wars, it's Roberta Gellis again, this time the Heiress series and the two add-ons (The English Heiress, The Cornish Heiress, The Kent Heiress, Fortune's Bride, and A Woman's Estate). This series spans the Wars, from the exploits of an English gentleman gunsmith trapped in Revolutionary France (300winmag, what do you know about Lorenzoni quick-loading pistols, circa late 1700s?), to another English gentleman soldier fighting the Corsican in Russia, to the Peninsular War. The Corunna retreat in 1809 is personalized, and if the privations of that forced march don't get you, nothing will. But give A Woman's Estate, which concerns an American woman in England in 1811-1812, a miss if you're looking for good fights --- it's a murder mystery more than anything.
If you like guns and the Old West, pick up Elizabeth Lowell's Reckless Love and her Only series (Only His, Only You, Only Mine, and Only Love). Set in the wild times directly after the Civil War, each book is a snapshot of the various folks who came West, and why. I especially like Reckless Love because of the horses, who are secondary characters.
Sheesh ... and you asked a simple question! I'm sorry ... I get verbose!
Basically, any blackpowder repeater prior to the Colt revolver was a "suicide special" for the wealthy. Somewhere inside the gun was a hugh reservoir of black powder, just waiting to blow up when the flimsy sealing system failed.
Revolver designs had been around for ages, but Colt came along at the right time. The industrial revolution was able to make precision, high-strength revolvers. It took another 25-30 years to learn to make the brass cases that provided the quantum leap in weaponry.