The Army M24 has a long action (unlike the USMC M40 which is short action only) and is already fielded in both 7.62 NATO and .300 Win Mag. This XM2010 is still a bolt rifle and a long action, so I'm not sure what the advantages of the new rifle are.
And by the way, there is a long history of military snipers making good hits at ranges beyond 800 meters with the 7.62 NATO. Granted, the .300 win mag will carry further, but don't short sell the 7.62 cartridge. 800 meters is merely deemed to be the "maximum effective range" for 7.62, but I have fired the Lake City 175 grain Match load used by the military in my Remington 700, and it is a pretty hot load. My own hand load which is not quite as hot is still supersonic at 1000 yards—at least on paper it is. If you get hit in the chest or head by a 175 grain bullet going 1100 fps in a steep downward track, it's either going to explode your head from the top down like a melon, or it's going to cavitate your chest on its way to your diaphragm.
So, in the hands of a good rifleman, a 7.62 NATO sniper rifle's "maximum effective range" can be extended by a couple of hundred yards. Beyond that, the magnum is definitely the better choice. It might be the better choice closer in too, but it sure won't be much fun to throw 100 rounds down range with one.
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