Re: EDM Arms M96 in 50 BMG or XM in 408 CT ?
If your goal is ELR shooting, both will cost about the same to feed and it will be expensive. The high performance solids needed for the .408 are about $2ea and while you can shoot cheaper jacketed lead bullets in a .50BMG, you're not going to get beyond 2000 yards accurately without moving up to higher quality (and more expensive bullets).
The .408 is MUCH more pleasant to shoot than a .50BMG but honestly some people just like having a .50BMG because it goes BOOM a hell of a lot louder. If that's important to you, then by all means head down the .50BMG road. Personally, I think .50BMG is best suited for military applications where you need either high mass bullets (ie stopping vehicles) or payload capabilities (for HTI missions). The .408 will get you farther and more accurate easier than .50BMG in that regard.
That said, as Later mentioned, the .408CT has been eclipsed by the .375CT - which stays supersonic out to 2800 yards vs 2250. Getting a Windrunner in .375 is a challenge though. If you realistically think you'll be shooting beyond 2000 yards regularly, then by all means go for the .408 - it's a VERY fun cartridge to work with. However, if you're honestly going to be staying under 2k, I would suggest moving down to a .338 Lapua Magnum.
One more important thing to consider is hand loads. If you do not already make your own match ammo, then the .50BMG is a better option as there is a WIDE variety of factory ammo available. The list of .408 factory ammo is fairly limited and expensive and the same goes for .338LM (though there are some less expensive options showing up these days). If you do your own hand loads though, keep in mind that .338LM can be loaded on much of the same gear as you would use for other rifle calibers. Moving up to .408 or especially .50BMG requires MUCH bigger everything - that means new press, trimmer, priming setup, etc.
Just stuff to think about.
