Arming the IRS?

I am a big fan of shotguns - love the Remington Wingmaster - but can someone tell me what the IRS is doing arming themselves with police grade 12-guage pump shotguns?

From the solicitation:

The Internal Revenue Service (IRS) intends to purchase sixty Remington Model 870 Police RAMAC #24587 12 gauge pump-action shotguns for the Criminal Investigation Division. The Remington parkerized shotguns, with fourteen inch barrel, modified choke, Wilson Combat Ghost Ring rear sight and XS4 Contour Bead front sight, Knoxx Reduced Recoil Adjustable Stock, and Speedfeed ribbed black forend, are designated as the only shotguns authorized for IRS duty based on compatibility with IRS existing shotgun inventory, certified armorer and combat training and protocol, maintenance, and parts.

Like Obama, I am not a constitutional scholar, but I don't remember a provision for armed seizure of assets to satisfy an IRS claim.  I fully understand that a perp might get violent, but that's what police and FBI are for. This by the very same people who want to limit our access to firearms?