I would say, the whole thing. But I’d have to sit down and measure one and scale each dimension if I were to give you a drawing. I would figure that somebody would have a program that might do that from a 454-423 bullet.
I am not a bullet designer by even the wildest stretch of imagination. I have been watching this thread and said to myself, “How difficult could this be? Well as I fumbled around with numbers it didn’t take long to see why the ones who do this have a computer program that takes all of the guesswork out of designing these things. The thing I came worked up looks like a NOE 432 255 and they are in the web store. Maybe it could be re-designed?
I would say leave the band lengths, nose length and overall length as is just make the diameter smaller by .021-.022 and it would be fine. I ran it quick through the mountain mold software and it should be about 220 gr.