I have some questions regarding the 318 W-R:

1.) What are the traditional groove and bore diameters for this cartridge? From what I can gather, the bore is .3180 and the groove is .3300. However, the barrel maker I am talking with thinks that the .3180 groove diameter is abnormally deep and that a .3200 groove would be a better alternative. (FWIW, the closest bore reamer they have is .3200 and they would then cut the grooves using the single-cut method.) This leads to my next question . . .

2.) Would a .3200 groove diameter be OK for the 318 W-R? This would allow for a .005" depth per side.

Thanks in advance.

Standard bore/groove diameter difference in most modern cartridges is about .008" but I can't think that a bore/groove difference of slightly more than this would cause any problems. I would guess that the original deeper grooves are a throw back to black powder days & shallower rifling with modern projectiles is typical. Its only .001 on each side of the bore & there are many cases of rifles being shot with greater differences than this to their "ideal" rifling size. Sensible load developement will take care of any pressure problems & as long as the bullet is a snug fit to the throat & bore accuracy should be OK.
Steve

You will probably get shit accuracy with a .320 barrel. The real secret to the .318 was (is) a very precisely-cut barrel and those shallow Metford grooves. Try .320 barrel, but good luck, I think. Its called a .318 for a reason, methinks.

I based my reply on the fact that Woodleigh bullets for the 318WR are .330" diameter. There was some confusion in pinotguys post about bore & groove diameter I thought & so I made the assumption that we were talking a barrel with a .330" groove diameter & a .320" bore diameter & with .330" diameter bullets this should work just fine, its not that different to shooting .308" bullets in a barrel with .308" groove diameter & .300" bore diameter, other than .002" tighter rifling which should not cause pressure problems. As to why its called a 318 WR, I'm not sure, but I've never heard of them having .318 diameter bullets, its no mistake that Woodleigh makes them the diameter they do.This chart of bore specs from GS Custom would tend to bear this out.It appears that .318 refers to the bore diameter as a lot of British calibres did. A .320 bore would be .002" less than factory specs but this is relatively insignificant.
Steve

I just went into my gunroom and opened a box of Knoch 318 Rimless (318 WR) and measured the bullet with a Starrett micrometer and dia. measured .329/.330 just to verify! Hope this is of help.

m4220

Just in case you don't know, Lothar-Walther makes barrels for the .318 and I believe Krieger does also.

quote:

Originally posted by m4220:
I just went into my gunroom and opened a box of Knoch 318 Rimless (318 WR) and measured the bullet with a Starrett micrometer and dia. measured .329/.330 just to verify! Hope this is of help.

m4220

Exactly what the ones in my collection measure as well.
Steve

YThe reason it is called a .318, is because the original diameter of the unrifled bore was .318"...i.e., the land diameter was/is .318".

The Brits, using cordite as a propellant, experienced very severe erosion of barrel rifling until they started considerably reducing the nitroglycerin content of their cordite. Though SOME successful black-powder rifling forms actually had quite shallow grooves, others had deep grooves. Anyway, the Brits soon found that deep grooves gave better barrel life with early cordite than did shallow grooves.

And, that .012" deep measurement of groove diameter over land diameter really is not that much deeper grooves than modern grooves for American nitrocellulose powders.

The .008" of American grooves (over the diameter of lands), is really the result of TWO opposite grooves, each measuring .004" deep.
Likewise, the .012" of the .grooves in the .318 barrel is really the sum of TWO grooves again, each of which is .006" deep.

Not exactly a chasm.