You are doing some beautiful machine work, Fred C!

(BTW - U.S. Model 1917 Enfields were an adaptation of the Pattern 1914 Enfield, being manufactured by Winchester, Remington, and Eddystone for Great Britain. The tooling, gauging and threads were to British specifications and design. The Krag and 1903 Springfield share a different ancestry than the U.S. made Enfields).

Fred C, before you start reaming on the .311 barrel, read about the 1917 barrels in Hatcher's Notebook.  The decision to standardize P-14 parts for US 1917 production included leaving the .303 barrels in production and simply chambering them for the Springfield case. 

A 1917 with an original barrel should shoot .311 bullets more accurately than they ever shot .308 bullets.  That is why they shoot so well with cast bullets.

WW2 2-groove barrels shoot OK because they only have half as many places for sloppy work.  Often the 4-groove barrels have 2 pairs of grooves of differing diameters.

The .276 Enfield cartridge was just a bit smaller than the .280 Ross.  That is why the 1914-1917 action is so big.

The 7X57mm Mauser rifle and cartridge sure got the attention of the British Military, during the Anglo-Boer War in South Africa. (and the U.S. Military during the 'Spanish War').

In the early 1900s, lighter Spitzer BT projectiles, driven at higher velocities, were replacing heavy RN bullets, for most of the World's military powers.

The Pattern 1913 'Enfield' rifles, produced in 'Trial Numbers' at Vickers, Ltd., fired a .282 inch, 165 grain, projectile at 2,800 FPS. As 'reincarnated' pointed out, WW1 stopped this development.

Vickers focused on making Machineguns! (Gauges, tooling, and blueprints came to U.S. manufacturers to produce .303" Pattern 1914 rifles on contract for Britain).

Photo of rare Pattern 1913, .276 Enfield cartridge packet, and comparison of cartridges:

In post #11 I mentioned that the reamer was being remade by PTG. I got the reamer later that month and asked some experienced gunsmiths about finishing using the corrected reamer and they said doing it by hand on an assembled barrel and action would be easy as it is done quite often.
So I made a brass extension to allow me to reach through the receiver, then a .010 thick shim to ride on the reamer to keep it from changing the head space. When I original threaded and installed the barrel the head space was set .001 over the minimum or go gauge limit and I did not want to change that. The shim stopped the reamer from advancing when the rim portion of the reamer contacted the shim.
You can see the brass shim stuck on the barrel face, the reamer turned with a little resistance till it hit the shim on the barrel face, then the turning effort went to zero. I had filled the recesses in the receiver with shredded paper towel and modeling clay to make the clean up easier.
With the area just in front of the rim at the correct size, new and resized cartridges chamber and extract easily.
Loads for this rifle were discussed in this thread and fixing the chamber should not change any of the data by more than a smidgen: (You need to Login to view media files and links)
If anyone is interested in doing another 35 Krag I would sell the almost unused reamer for 1/2 price.