Good friend received a Ruger American in .450 Bushmaster for Christmas. The ballistics approach the black powder .45-90 with a 300 grain bullet and it would be a good choice for elk in the hills and valleys of Western and Central Washington. Owning a dozen or so .45 caliber rifle molds, I told him we were ready to try anything from 300 grains to 540 grains.
Enter the dark cloud, the .450 Bushmaster has a .451 bore, not .458. The heaviest mold .452 diameter mold that I have is a NEI SWC at 270, plain-base. Off to the web to find gascheck mold (RCBS 45-300-SWC), brass and people's experience with reloads.
The mold arrived and cast beautifully after cleanup. Experimented with pot temperature and ended up at 775 degrees, the bullets cast evenly between .452 and 453 diameter, sized .452; the gascheck shanks fit firm when seated and now we need a decent range day to see what the groups are.
Farm boy from Western Illinois, living in the Magical Pacific Northwest