Winchester 1873 with 16 inch barrel.
when that rifle was designed, lead bullets were all there was. And, it wasn't offered in .45 Colt until modern times, the .45 Colt ammo of the day wasn't felt to have enough rim for reliable function. Today, that's not the case.
I don't know about Winchester designs but I know why SWCs don't "play well" in Marlins, its usually a slightly misaligned round on the carrier allowing the "square corner" of the bullet (right above the case mouth) catching on the edge of the chamber. The "fix" for this is operating the lever at the right speed, and if it hangs up, not forcing it forward, but backing it off, so that pressure if off the jammed round, which then (usually) fall back into line to be chambered normally.
Using flat point or truncated cone bullets is fine, if they don't have the SWC shoulder to hang up on.
Overall length is important. Rounds that are too long will not feed from the tube through the action. Some guns are more picky about this than others. Generally speaking, at or slightly below listed max length should work. Too long rarely does and too much too short can cause issues as well.
My experience with lead bullets in over 40 years of shooting is that when the lead alloy, velocity and fit in the barrel are all properly balanced they don't lead to any significant degree. But when any or all of these factors aren't correctly balanced with each other, they do lead, and can lead badly.