Go/minimum dimension on the .30-06 chamber is 1.940. No-go/max dimension is 1.946. Field/reject dimension is 1.950. The 1.940/go/minimum dimension must always be established and verified before firing the rifle. The 1.946 no-go/max dimension is the tolerance to be used when fitting a new barrel as this allows for progressive wear on the bolt lugs and lug seats as the rifle is used. The 1.950 field/reject dimension is used for rifles in service and is just that. If a rifle "fails" a headspace check on the field/reject gauge the barrel must be replaced, unless a longer bolt can be located which will bring the headspace below 1.950 as determined by the field/reject gauge.
The Clymer pull thru finishing reamer will cut a 1.940 chamber, altho this can be adjusted to a greater length by using a custom dimension thrust bushing against the bolt face while cutting. I've used the Clymer finisher to cut quite a few chambers in new Garand and M1903 barrels and find that it does a very good job.
The maker provides detailed instructions on reamer use, incl the importance of using a good cutting oil, not crowding/forcing the reamer while cutting, the importance of not reversing the reamer in the chamber, the need to protect the reamer cutting edges when not in use, and cleaning cuttings from the reamer during the process of finish reaming. Clymer states that their reamer should cut 100 chambers before needing to be returned for re-sharpening.
The Clymer pull thru reamer set up from Brownells is currently priced at $216. If you aren't careful with it you run the risk of dicking up both the reamer and that $300-$400 new barrel. I would not loan my reamer to someone else.
Barrel installation is always a concern as too much torque can damage the receiver. A barrel that sits too far off index when hand tight needs the shoulder to be adjusted on a lathe. Conversely, a barrel that is too loose at the starting position requires that it be roll swaged to displace some metal to the rear. You can avoid these measures by selectively trying various barrel/receiver combinations, but that assumes that you have a number of receivers and barrels on hand to play with. If you are using just one barrel with a particular receiver it is a bit of a crap-shoot on proper fit. I've read a few DYI accounts about how people claim to have adjusted a loose barrel shoulder by peening the circumference with a hammer or by trimming back the barrel shoulder with a file, but I would not want to own a barrel that had been dicked with like this. Just imagine the dimensional inconsistencies.
When you consider the outlay for a new barrel and a finishing reamer it is preferable to have someone who has the proper tooling, knowledge and experience do this for you.