It's called a Rem 700 Bolt body cutter. It cuts the recess on the rear of a barrel .150 deep and faces off the back at the same time so you don't have to set up to a tool bit to cut the recess.

It comes with removable pilots, and also can be used to square off the muzzle prior to crownng.

I was really impressed with the one I have been using.

call Dave or Dara at 810-953-0732

I've had one since 1994. Got it from Clymer when Dave was still there.

I don't see how this tool would be any faster than cutting the recess with a tool bit.
The tool bit also allows you to control the exact diameter too.

Makes it about 3 times faster for those of us who use a lathe, and eliminates one source of possible error. For those who don't use a lathe, it's the only game in town.
Regards, Joe

Touch the tool to the barrel breech.
Lock the carriage.
Lock the micrometer carriage stop against the carriage.
Back up the micrometer .140.
Unlock the carriage, rough out to depth and diameter. Stop about .010 under the bolt dia.
Check depth and diameter.
Back off the micrometer about .010
Face the c'bore until you touch the ID
Move back out of the cbore turn the cross slide out to finished dim
Bore the ID of the cbore.
Check that it is good
Polish.

I bought one from Kiff/PTG at least five years ago.

Like I said, about 3 times faster and less chance of error. Obviously you're not in agreement with the majority of responders here.... or elsewhere, for that matter (G).
Regards, Joe