Something to be aware of when choosing a mold for a Marlin Lever gun (any tube fed lever gun for that matter) is that a lot of molds are made for the Single Shot buffalo rifles and they have a nose that is too long to feed thru the mag, they can still be shot thru a Marlin but must be fed one at a time thru the ejection port.
I would suggest a flat nose 405 gr or less , round nose are usually too long between the crimp groove and nose...even some of the flat nosed slug molds over 405 have been too long to feed thru my Cowboy.