The 460 might work with a magnum bolt head, and for that you would need a pushfeed Magnum bolt head for the short action, or modify a long action magnum head to fit the short action.

With the 450BM you would use a standard 308 sized (.473") bolt head. If you are planning to reload the 450BM can be loaded to easily surpass the 460 by a good ways and still be totally safe and brass friendly in a bolt action. Jim at Apache Gunworks is the only one I know of making the 450BM barrel and Jim does top notch work. I have 4 barrels built by him and will have plenty more in the future.