I would second the slug gun suggestion if you're craving or needing some real punch now and then. Nobody I've ever met or talked to has ever said "yeah, had a nice afternoon of shooting my 45-70 today". It's a few shots here/there so you could justify the cost of shooting 45-70 or scratch the itch shooting slugs.In all honesty, this will just be a range toy as it will not offer any real performance down range. Groupings at 100 yards would be more like patterns. I'd imagine it would be fun though, tossing some good fireballs. I would consider a different brand though
While it would be a fun range toy/attention grabber....I'd take the advice given a number of times=get a longer barrel. Personally, I pay no attention to 45-70 unless the name Marlin is attached to it but I have no first-hand experience shooting anything else in that caliber.