You (and others) seem to be proceeding to a false assumption - it's not my interpretation - it's the loophole these govt organizations are exploiting to buy our all the ammunition on the market - a loophole that they would
use if it did
go to court. Yes, there are certainly a lot of scared citizens buying stuff too, and the dealers are also intentionally hording the ammo, artificially inflating the prices to exploit the prevailing fear, but even they have been running out of everything eventually. If you can't control the guns, control what you can shoot out of them, and they've been quite effective, while simultaneously contributing to the same mass paranoia that the govt decries.
And it isn't just the IRS doing this. DOE and DHS has been doing it for years now, just under the radar. When the recent anti-gun legislation earlier this year failed, DHS in particular really stepped-up their purchasing efforts to a degree that actually did give Congress pause and a raised eyebrow - it was all over the news (not just conservative blogs), sprinkled with the ubiquitous poo-pooing and allegations of unfounded paranoia. The purchases seem to have recently dwindled due to sequestration limits, which I find mildly amusing (and ironic).