Dan,

In a gunnutshell:



The 45 Lapua is simply a necked up .338 Lapua Magnum, hence has a .416 Rigby-sized case head and rim, and, externally, exactly matches the .416 Rigby up to the point where the Lapua shoulder starts. Internally, the Lapua brass is heavier, stronger, thicker in the web, than standard .416 Rigby brass.



The 460 G&A and 450 Vincent Short and Long are all based on the smaller case head and rim of the .404 Jeffery cartridge. The short version has a 2.5" case and the long version is about 2.8" IIRC.



The Lapua is an intermediate length near 2.7".

The Lapua has a 20 degree shoulder semi-angle, and the shoulder is broad enough to draw no giggles. The neck is very close to 0.45" long. Adequate.



The 404 Jeffery case is marginal for a .458 bullet, regarding shoulder. The Lapua/Rigby is not.



There is no finer brass than .338 Lapua Magnum Brass, and if you shop around, you can find it for about $1.40 per pop in the USA.

Thank you Dan. There are no flies on this one. It is a wildcat that has probably been knocking around since the .338 Lapua first came out in 1987. I wonder who did it first? Any new brass soon gets necked up and down by somebody. Why not neck with the best? Lapua .338 Magnum. Thank you Finland.