If I'm not mistaken (which has been known to happen ), the Federal Protective Service still issues revolvers. I was in a Federal building in Boston a couple of weeks ago for an interview and the FPS officers on the door were all wearing revolvers. I think I saw three Rugers (GP100) and two SW Model 10/64. The FPS is charged with guarding Federal Buildings and Courthouses. The Federal Building in Honolulu, HI (I was living out there till last year) is protected by FPS armed with revolvers. I'm not sure what round they are issued, though I believe based on conversations with a couple of the guards that they use the "FBI load."
Doug