You can fire a .45LC in a .410, but with no rifling it won’t be very accurate. A .410 in a .45LC can damage the rifling if I remember correctly..45/.410 pistols usually have maybe an inch of rifling, then the rest is smooth barrel. A complete smoothbore pistol would be illegal unless you pay the $200 NFA tax on it, so the inch of rifling is for legal reasons. I’ve always wanted to get some of those Leinad .45/.410 kits to built. They’re like $40 each or less in kit form! Then you just need to make the breech face and frame and weld it. A couple other neat .45/.410 pistols are the
Thunder Five and the
Bond Arms Derringer.
The problem with running .45LC out of a .410 barrel is that a .410 barrel is usually full choke because of the limited number of pellets. So you may have an obstruction issue.
As far as running a .410 out of a .45LC goes, the pellets need to be soft lead. If you run soft lead you won't damage the rifling of the barrel. You may foul the rifling and it'll need to be claened throughly, but you won't damage it as the lead is softer than the metal of the barrel.
