Help me design a cast bullet

[RAC]

I have a WWG Co Pilot/Marlin 1895 45-70/457Magnum. The 457 Mag is
just a lengthened 45-70 case 2.205 inches long--a tenth of an inch more
than the 45-70. Personally, I would just rather shoot 45-70 cases in my
gun but with an over length of 2.650 inches instead of the original 45-70's 2.550 inches. I have designed a 405 grain Gas Check Ogival Flat Point bullet on Mountain Mold's online bullet design site for this purpose that has a .550 inch nose length. This nose will be a tenth of an inch longer than standard.  I want a bullet of .460 diameter after sizing with a 75% meplat. It will have 3 body bands/2 lube grooves with the front band's diameter a couple of thousands smaller than the other bands. This is the first time I have tried anything like this and I was curious if anyone with more experience than I would have anything else to add.  Thanks.  Roger

[Leftoverdj]

RAC, there are those who know far more about this than I, but I have some comments. My view is that for a cast bullet to shoot well, it needs twice the bearing surface that it has nose. You are also going to have to be very careful about your pressure in relation to the strength of your alloy. A tenth of an inch plus a bit is going to unsupported at ignition. Too much pressure and bullet will flow into that unsupported area and either recompress or be sheared off when it hits the leade. I'd put that tenth of an inch into a full diameter bearing band to get it into the existing bullet seat.

Even simpler, I would take a chamber cast and send it to Dan with a basic description of the situation and trust his judgment on what is needed.

[RAC]

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.