The only reason the 500/450 is not more popular is because it was an H&H properitary round, ie not released to the trade, and thus only avialable in expensive H&H doubles and in not many of them because of the ban.

It is a good cartridge.

I have and use quite a bit a 450 No2. The case is larger than necessary for modern powders no doubt as you MUST use some sort of filler with any powder that I know of. But it is very easy to load. I really like the necked case over the 450 straight case and the thick rim is a big bonus as well.

I have yet to ruin a case and some of mine have been fired at least 25 times. And this is Bertram Brass.

I also prefer the .458 Bore over the .470/475's.

However since Hornady will be loading the 450 3 1/4" Nitro Express, that is probably the best way to go today in a .458 bore double.