Here is the final stage of barrel fitting, chambering. This barrel has previously been threaded and breach cut to fit a Remington 700 Titanium, as can be seen here. This barrel will be chambered in .270 Weatherby. These are the tools required:
In this case a JGS ground .270 Weatherby reamer, PTG Belted Magnum gage set, and a dummy cartridge. The dummy cartridge is not normally necessary. In this case I am building a new rifle to hopefully be compatible with ammo loaded for another and a dummy cartridge will allow me to correct any fit issues right away.
Making chips. It is interesting the difference cartridge design and proportion make for to the feel of chambering. The .270 Weatherby is fairly large body diameter in relation to the bore size, a lot of metal has to be removed to clear the chamber. An example of the opposite proportion is the .300-221 Fireball, very little metal to remove in either diameter or length of the case. The first one I cut I nearly blew past the headspace the chamber cut so quickly.
As soon as the belt portion of the reamer hits the breach, I clean off all the chips and test fit to get a measurement for final headspace. You see the action, with bolt closed, screwed down tight against the GO gage. The gap between the barrel shoulder and recoil lug is just about .060″.
After the bolt closes on the GO gage, and in this case the dummy cartridge which needed a bit more then zero headspace to fit, I check with the NOGO gage to ensure I am still with in the tolerance of the belted magnum cartridges. And this barrel is now chambered, next will be fitting the barreled action to a stock.