The Fed’s would use M40 or M110 class rifles in 7.62 or additionally the option of 300 winmag for the M40 some might also have larger 338 Lapua mag typically the Ruger precision version which is also what the U.S. military uses. They all source from the same GAO contract sources. 270 would not be a caliber used. Every one of those rifles is factory tested and certified for submoa the Ruger is rated at .25 MOA or better from the factory.
The IRS has all that?