Hello everyone, let me start off by stating that I am not experienced whatsoever in the field of bullet casting. However, I do plan on launching the Missouri Bullet Co 255gr. Keith Bullet (BNH 18) out of my .454 Casull. Now I am wondering how fast I will be able to push it without causing leading or harming the forcing cone. Is there a rule of thumb that dictates which hardness fits which velocity? Thank you!

Looks like you missed probably the biggest variable. More than the others what about how those bullets fit in relation to the chamber throats, bore diameter? Also how are you loading them? Is an expanding M die being used in the cases, so your not squeezing the bullet heals down? All of the fits must be correct for best results. The best thing in the world is to start measuring things and look up the necessary information to know how these are supposed to fit

I would add that shooting powder coated bullets makes life a little easier. Leading is alot less common across the normal velocity range, especially if they're sized to fit your throat.

You will find your rule of thumb here:
http://www.lasc.us/CastBulletNotes.htm

Thank you for the answers. I'll have to look into the whole throat diameter affair, never considered that. Looks like I won't have many problems pushing the Missouri bullet to .44 Mag velocities provided it's properly sized.

A few years back Ruger revolvers were notorious for tight cylinder throats at which p

Point hard cast bullets don't help if they're running through. 449" throats before they get to a .451" barrel. If you really want to run fast with cast bullets then I highly recommend gas checks. You'll not be able to get them going too fast out of a 454.

I have shot cast bullets from my 44 magnums for years at a Brinnel hardness of 16 without gas checks and had no leading problems. But, I’ve always made sure that sizing matched up with my revolver throats and bore size.