I always thought that the ring around the case was for makeing sure that when loaded with a jacked bullet it did not get pushed back into the case when using in a repeating rifle such as a 1894 Win., had nothing to do with the powder, at least that's what one of the guys at Winchester told me many years ago.
ST

    Thanks Guys;

        Set Trigger, the ring imprint around the case is very slight, and the inside indentation is not much, but I guess it could be intended to be an "index mark" for seating long jacketed bullets.  The ring in set back away from the mouth at  0.540 ", so you may well be correct.

      What I understood was that Winchester didn't want their smokeless loads  winding up in the multitudes of early black powder firearms when W-W first switched over to smokeless and they were producing both Smokeless and black powder simultaneously.   

Each box of ammunition would have been clearly marked to distinguish one from the other, but W-W apparently wanted something in the way of a permanent "mark" on higher pressure smokeless cases for when they were placed into a cartridge belt or sportsman's pocket.

Someone must know for sure  (Winchester Manufacturing obviously does)

Creedmoormatch

I consulted Shuey's "W.R.A.Co. Headstamped cartridges and their variations".

There was a short range load with a 98-grain lead bullet loaded from 1894 to 1916.  Also from 1912 to 1916, a 100 grain "full patch" bullet was loaded.  Both loads apparently have a small ring near the neck.  The black powder load without any grooves was loaded from 1886 to 1937.  The smokeless load with the groove at the base of the bullet first appeared about 1895 and was apparently used throughout the WRAco production run.  The groove was on the case regardless of whether the case was sold as reloading components or loaded ammunition.  I have some new "Winchester" cases that came from some factory in a factory-labeled zip-loc bag.  They have grooves.

The groove served to stop the bullet from being pushed back into the case when loaded into a tubular magazine.  I was also told by a retired W-W employee that it was an easy way to quickly identify a product in the midst of a manufacturing run.