Why don't you do a little research instead of whining on the internet about how there's no legit use for that many rounds of ammo? No you have no clue what it takes to ensure we have highly trained federal law enforcement agents and apparently you can't be bothered to lift a finger & find out...
Well, here's a start for you....
http://en.wikipedia.org/wiki/United_States_Department_of_Homeland_Security#Structure
Customs & Border Protection (CBP): 21,000 Customs Officers, 21,000 Border Patrol, 1,000 Interdiction = 43,000 armed law enforcement agents
Immigration & Customs Enforcement (ICE): 8,500 HSI agents, + ?? ERO agents (no # listed on wiki, but figure 2,500+ since they operate nationwide) = 10,000+ armed law enforcement agents
Federal Law Enforcement Training Center = training site for over 90 Federal Law Enforcement Agencies.
So you have right there in 5 minutes, over 53,000 armed law enforcement agents, all of whom must complete mandatory firearms training, and plenty of whom probably do extra training. Then you've got service weapons, armories and such to stock in case of emergency. Oh and then you've got a large training center that includes a lot of range time.
And that's not even counting the Coast Guard or the Federal Air Marshal Service or the Secret Service. You don't think the Secret Service guys live at the range when not on detail?
And finally when your life is potentially on the line (or the lives of citizens you're trying to protect) You Train as realistically as possible - which means becoming intimately familiar with the operation of your firearm with it's service ammunition.
Gimme a fuckin break.