Just doing the math...it seems like there must be plans for DHS to add a whole heap of operatives. Training can involve simulations, then work with 22 shorts, and then full calibre weapons. 450 million rounds of full calibre ammo is a hefty order indeed.
Not this again! They are not buying 450 million rounds. It is basically an open contract. When they need rounds they can order them from this vendor. It is like the vendor is preapproved contractor for selling bullets to DHS.
Even if they were buying that many rounds. Split up between every DHS employee, it probably would not cover their training. The army probably buys billions of bullets each year.