Winchester Magnum Rifle ball powder was introduced in 1994 and discontinued a couple of years later.
It was useful in 243, 257, 25-06, 270, 280, 300WM and 338WM cartridges. No current information online via
Hodgdon, but in other US forums, users report it is similar to the newer W780.
If you can find a Barnes #2 or # 3 Manual, there is some WMR load listed there. Alternatively, try and
locate a mid-'90's Winchester data booklet ... a local dealer or gunnut/reloader may have a copy tucked away in a file somewhere.
You might try a PM to "H4831" on this site. Time and again he seems to have access to some of the older data.
