Thanks for the replies.

From another site, dimension of the .318 case length is given as 60.7mm, splitting the difference between the x57 and x63 cases. Appears it would be, as you guys say, closer to a mod of the .30-06 case than the x57 case, and since {I believe} the .318 preceeded the 8x60 that is a deadend for its origins. And yes, it appears, if this length dimension is correct, .318 cases could easily be made from '06 cases as the base diamter appears to be compatible.

Anybody have an actual case and bore/groove they can or have measured?

The 180 grain weight was, as I understand it from the printed material, a "standard" bullet weight along with the 250 grain, fired at 2700 fps, as you gents say, duplicating .30-06 velocity {but with a bullet of lower sectional density}.

Taylor mentions that the cartridge was a development of the 7.92 Mauser {8x57} and indeed that is what the cases appear to be in photos I've seen but the dimension above belies this. I have never seen a .318 standing next to an 8x57 and .30-06 to make a visual comparison. The .318 certainly offers a pressure advantage over the 8x57/.30-06 with the heaviest weight bullets {a 250 grain weight generates higher pressures in the 8x57 for the same velocity} though again with bullets of equal weight the 8x57 or .30-06 have higher sectional densities.

Anyway, I'm curious as to actual bore/groove diameters of a sample rifle and actual chronographed old-time factory ammo velocities, too, if anybody has this info. Looks like an easy cartridge to resurrect as even in the absence of factory .330 diameter bullets .338's should be easily sized down just as I do reducing .375 bullets to .366.