dirteemax,
jimmym40a2 has some of those calibers and access to the others. If you want someone with real world experience, he is your best resource on here.
However, that analysis is with custom projectiles that may or may not be available up here. The results may be different depending on the BCs of the bullets you can get.
If you really want a 416, you're best to see if you can actually get high-BC bullets in .416 here and then design a chamber reamer around one of those and also look into a reamer for making the dies. If you can't find anything, there is always the swage-your-own route...
All the cnc machined bullets are available on barretts website and wolverine supplies can get the bullets and brass rite from barrett. I have some of the barrett 416 brass sitting here rite now. The hornaday bullets can be ordered by any hornaday dealer in Canada.
So i think the good CNC machined bullets that he was using in his comparison are probably available up here as it is not illegal to export 416 from the states like it is with 50bmg
RCBS makes reloading dies so does Lee and it sounds like the guy at M2 precision may start making some "competition" reloading dies for the 416 as well. So getting the reloading supplies seems like it's going to be much easier and cheaper then getting 50bmg stuff.
Though I think the 50cal is still king of the hill so to speak. I'm just interested in trying something different that's all.