the 300 Win Mag, is the most preferred cartridge for U.S. government snipers
I believe you're way off base on this one. I've read that the Army was experimenting with 300 win mag in A'stan. But I've not read that it actually has gone mainstream.
From everything I read now days they use recon/sniper teams as spotters/illuminators for air power, predators, cavalry, etc... Not really doing a whole lot of one bullet kind of stuff. Just the occasional target of opportunity.