Samuel Colt- The grandfather of the firearms industry. He revolutionized the way guns were manufactured, proving that a firearm could be mass produced and still maintain high quality. Just know that there’s a little Sam Colt in every revolver you see.
Elmer C Ballance – Springfield Armory, the M1A. Maybe you’ve heard of them? Yeah, you have.
Richard Gatling – The Gatling Gun. The one he invented was hand cranked. Now they’re powered by electricity. Get this, he invented a gun that shot such a high volume of leaded freedom in the hopes of cutting down the size of armies, their exposure to combat, and disease resulting from wounds. Weird way to look at things, but hey, now we can shoot 6000 rpm.
Benjamin T. Henry – In 1860 he patented his lever action, repeating rifle, the Henry. The design saw limited action in the Civil War and then found its way to the frontier where it helped settle the west. It did see action at Little Big Horn, not with US troops though. Custer was on the wrong end of the Henry.
Christian Sharps – The designer of the Sharps (duh) rifle. The falling block rifle originally came chambered in .52 but was changed to .45-70 Government around 1873. These things, in the right hands, could reach out and touch you at 1000 yards. No kidding. And some early models came with a coffee mill in the stock. Yes, really.