The .50/110 was designed for the Model 86 Winchester, much stronger even in the black powder version, than the Colt Lightening. There was a later smokeless powder load for the .50/110, which drove a 300gr. bullet at 2,200fps, same as the later and smaller cased and smaller diameter .405 Wincheser. The .50/110 was a powderful round, just not very accurate due to the ridiculous 56" twist in the Winchesters.

Too - it and the .50/95 were the laughing stock of the plains, amongst the buffalo hunters, due to it's poor accuracy and penetration from it's light for calibre bullets. Instead of rescuing the .50/95, the .50/110 had more of the same problems. The too-slow twist may have had a part in that, as the bullets would not remain straight-on after impact due to instability, barely able to stay that way in the air. Even 48" and 56" are round ball twist rates, perfect for a 175gr. to 180gr. .490" to .500" ball, not a 300 to 350gr. slug.

The .50/95 a black powder only round, was designed for the model 76 Winchester, and may have been chambered up in the long chambered Colt Lightening - I'm not sure. I suspect the .45/75 Winchester might have been, also a Molde 76 Winchester round.

Maybe the Lefever action is just fine - I don't know, but envision a wierdly latching mechanism for some reason that doesn't seem very strong to me.

This vision of what I think I envision as a Lefevre might be way out in left field.