Thought I'd describe a bit of the process I use when I'm trying to design a new cast bullet to suit a particular rifle.

This one is for FATBOY404's 404 Jeffery.
He wanted to try some cast bullets in his rifle, to make practice a little cheaper than shooting Woodleighs all the time.
The first thing we did was to do a chamber cast of his rifle, the casts were done out of sulphur, as it is easier to use and shrinks very little, if anything at all. Two cast were made, as sulphur is brittle, and it wouldn't have been the first time I've broken one.
A piece of cleaning cloth was inserted from the muzzle until about an inch from the chamber mouth, we wanted to cast the throat and a bit of the rifling to measure.
The throat of this cast measures 0.424" in diameter, and the grooves measure 0.423", about what you would expect for a 404. As near as I can measure, the throat is 0.100" long, until the point where I can see rifling clearly.

Here is a pic of the casts.

I'm going to use Mountain Mould most likely for this one, as they have an online design program where I can play with diameters, weights, nose shapes, front band lengths etc.
This pic is one that took about 2 minutes to design, not saying it is what we will use, but you can get the idea.
It is a 425 grain bullet, without lube or gas-check.

I have made the gas check shank on this one a stepped shank, I like these shanks, as the check tends to crimp over the ledge, making it nearly impossible to get off.
The nose length on this one is 0.600", with a 0.090" front band, 10 thou shorter than the rifles throat, to allow a bit of clearance for fouling etc. It has 2 nice lube grooves, to carry plenty of lube, and requires about a 1~17" twist to stabilise. As cast diameter is 0.424", and the front band diameter is also 0.424". Both these measurements are able to be changed to suit. This bullet has a 70% meplat as well, I don't want to go much smaller, as the nose tends to be a little unsupported on these bigger bullets.
This is a start, when we have decided on a final shape, weight and other measurements, I'll post a progress report.

Kind Regards,
David.