Thanks for the comment. I may be better off with a conventional 405 gr boolit and load it to 2.550 inches. It is not like I need the extra case capacity by loading it to 2.650 inches. I am looking for around 1800 fps. As long as it shoots accurately in my gun it really would not matter. I shoot Rem 405 grain bullets and have loaded them to the longer 2.650 inches with 45-70 brass. I would hate to go to the expense of a new mold with a longer nose and find out it would not shoot. However, this is what Dan had to say:
"A 0.550" nose is not really very long by rifle standards, and I am guessing that part of that nose will be bore riding, so bearing length shouldn't be an issue."
He does say that he is not a Marlin expert, though. It will be an interesting project if I want to risk about $100 for the mold. Who knows, I may do it anyway.