45 LC brass is quite strong. I loaded Starline 45LC brass quite heavily in a 454 and it stood up well to high pressure loadings. I think it will come down to how tightly chambered the rifle is.

FYI 454 brass takes a SR primer and a lot of people lament that change as ignition is better with a LP primer. I don't have any experience with 460 brass but they may well have thicker sidewalls which may not make it so attractive to use cut down to 45LC size.

These rifles are quite strong and I think you should be able to get a considerable performance boost compared to factory loads. Just be aware that a steady diet of heavy loads will test how that mag tube is attached and is something to watch.