Just to possibly add a little more confusion I have a Jeffery barreled rifle that was proofed at the London Proof House with the under barrel proof stamps of 360 EX and Cordite 30 - 300 Max. Jeffery nicely spelled it all out on top of the barrel with 3 lines: 360 2 1/4 case; 30 grains Cordite; 300 grain bullet. As you might expect, shooting a 300 grain bullet with a 30 grains of Cordite equivalent load of Reloader 15 in a fairly light rifle does get your attention but it shoots to the sights. I use exactly the same brass as I use for my 9.3x57R (360) Husqvarnas.
