.284 inch equals 7 mm in the United States in a Winchester rifle.

NOT .248 ---- BUT .284

http://www.gunbroker.com/Auction/ViewItem.asp?Item=118472625

Check out the pictures here of a .284 Winchester Model 88

In my very limited experience it is very rare to find the actual rifle caliber marked on a Hammer Drilling. I own 2 of them, neither of them are marked with what they shoot. I own a cape gun, it is not marked with what it shoots. I have learned how to cast chambers and throats to determine the correct cartridge to use. Jent