G'Day Fella's,

Harold, I have a Win Mod 70 Classic in 7mm Rem Mag.
From what I can see with my rifle, the action is long enough for a .375 H&H cartridge but as Daryl S mentioned, the magazine box has a shortening block at the rear for the 7mm and .338Mag size cartridges.

You could try drilling out the spot welds that hold the shortening block in place, get a Win factory mag box to suit the .375 H&H or I think www.wyattsoutdoors.com make and sell longer than normal box magazines to suit.

Hope that helps

Doh!
Homer