Marlin 45-70 CB rifle, the rifling is Cut type, not micro groove. It will shoot with jacketed or cast bullets. For a 45-70 I prefer the octagon barrel. You can have the barrel or magazine custom cut to any length you prefer. It doesn't have the ports that blow your hearing out when your hunting and don't have ear plugs in.
I have 2 trapdoor 1884 models, 1881 Marlin I use the most. It has 28" oct barrel and 1/2 magazine and double set triggers.
Depends on if you want lots of power go new. Like old time find a antique or copy of one. And if you intend to reload or shoot factory ammo.
Choices in some what chronological order:
US Springfield trapdoors, Remington Rolling block, 1874 Sharps single shot, 1881 Marlin, 1885 Win. S.S., 1886 Winchester, Marlin 1895 original version with square bolt, new 1895 Marlin with 336 action round bolt, and the Ruger No. 1 models.