Interesting info about the 300 Sherwood,

"In 1900, Greener introduced a cartridge called the .310 Cadet and a year later, Westley Richards came out with a lengthened version of the 300 Rook cartridge which they named the .300 Sherwood. Kynoch, who loaded ammunition for it, called it the .300 Extra Long. "The .300 Sherwood launched a 140-grain bullet at 1,400 fps, a considerable gain over the .300 Rook (80 grains, 1,100 fps) but a slight gain over the 310 Cadet (120 grains, 1,530 fps). (The Greener round developed more energy at 624 ft/lbs to 610 ft/lbs.)

http://www.ammo-one.com/300Sherwood.html

http://www.ammo-one.com/British-310Cadet.html

http://www.ammo-one.com/British-300-295Rook.html

However, the case of the 300 Sherwood being 1.54 inches to the 310 Cadet of 1.075 inch you have considerably more case capacity to load the round up.