Yes, and you will have a headspace gage for the .460 G&A.
Use that in your shortened .450 Rigby die to set the headspace when neck-sizing your fire-formed .460 G&A brass.
Foolproof.
I have done such with a .264/.375 Ruger using a Manson headspace gage for my pet wildcat,
called the .264 Ripmore or 6.5 Ripmoor depending on company present.
If you get the .375 H&H boltstop/ejector in there, it will be timed to eject 3.6" loaded cartridges,
loaded ammo bullet nose will clear,
you will not have to do anything to shorten the rear bridge or lengthen the ejection port.
If you find a source for .375 H&H M-70 boltstop/ejector, let me know.
I could find a use for some of those.
Last time I filed and stoned one myself, to get a .270 WCF M70 Classic action to eject .400 Whelen 3.6" ammo properly.
File a little, re-install, try ... uninstall, file, install, try ... uninstall, file, try ... Success !
I'd rather buy them ready-made too !
