Modern rifle ML conversion. Why not?

[GWP]

Thanks for posting that! I did not see that when I was looking at them. Interesting.
I wonder what criteria they use to determine 'modern'? There must be a definition somewhere. Anything that is 'capable' of using an enclosed complete cartridge I suppose.
You are probably correct in that there must be a plug, or something making it incapable of firing a complete and enclosed shell, but, would 'temporarily' qualify? Where you maybe needed tools to remove it? I would argue that the 'new, modern' muzzle loaders are about as modern as you can get. Particularly with the new powder, systems and using primers for ignition.
On the vid, that looks like a Winchester Model 37? Spring ejector. Same as the Model 24 SXS had. If it got dirty or the brass on the hull expanded too much they won't eject. I have a chunk of brass on a keyring I used to carry just for that purpose!

[GWP]

I will look further, but at this point, scouring the regs, I still don’t see a ‘modern’ as opposed to ‘loaded from the muzzle’ definition that would prevent using a thick walled case and loading from the muzzle.
Keep in mind I don’t actually plan on doing this... just playing the ‘What If?’ game.

[follow maggie]

So here is a concept. Since a 45/70 was originally a black powder weapon why couldn't you load a metallic cartridge an call it good 😤

Because that cartridge is loaded from the breech, not the muzzle.

[GWP]

Talking about ‘thinking outside the box’ and staying within the regs.