Good Job !
Looks like the 450 has a good throat. That will make life easier on you and on the bullet. A full diameter ogive would probably work, or else you could step down to 0.451" after a 0.190" long front band. Hint: at the bottom of the design page there is a number called "rifle throat length". This is the estimated throat length required for that particular bullet design. Understand, this is an output, not an input. Anyway, when designing the 450 bullet, you'll be OK as long as you keep an eye on what the "rifle throat length" says. That number is just a crude estimate, that does not take into account the exact dimensions of your barrel, but it will get you in the ball park. It does not apply to revolvers, however.
If your 480 rounds are 0.5026" OD with a bullet that is approximately 0.474", then a 0.479" bullet would increase the OD to 0.5076", and that wouldn't fit in your 0.5072" chambers.
0.477" might work, but there would be no margin for error. Looks like 0.476" is the best you can do. I'd chuck the Hornady crimp die, or else hone it out so that it doesn't damage your bullets.
If you are going to be shooting 0.476" bullets in a 0.479" throat, then you are free to make a 0.476" diameter front band as long as you like without worrying about chambering problems. Whatever tickles your fancy.
It's just amazing that our guns shoot as well as they do, considering all the funky dimensional imperfections.