You can still biy CZ 416 rigbys. Rebarrel it to 450 rigby. Brass is available with RavenRock.Wouldn't matter if they worked or not as long as you're not hunting DG with them. At half price and the cost and scarcity of 450 Rigby brass you're way ahead even for once fired brass. They're STILL $80/box along with 500/416NE. And .416 Remington at $85/box. Less than .338WM IF you can find those! Since my DREAM rifle in .458 or 500 B&Ms are now apparently unobtanium, I thought about buying a case of the 450 Rigby. But now even the CZs in that cartridge seem to be MIA at any reasonable price. Sucks to have gotten into the African large bores a few years too late. LOL
It is not too late if you want one.
Krish