Some time ago I was on the lookout for a 458x1.5 die set, to size 458x1.5 brass. After a few months, it doesn't look like I'll ever find one. Running it through a 458 WM sizer doesn't put the right taper on it, as the mouth is .458 WM, the base is .458 WM, but over a 1.5 inch case, which gives it a steeper taper. Along the way I picked up a 458 Win Mag die set, with the idea of cutting the sizing die down, but after measuring, that plan won't work for the correct case size at the belt. Looking at the 458 WM brass, It looked to me like a 375 H&H blown out and shortened, so I took a vernier to a fired 375 case, and the case diameter at the 1.5 inch mark on a 375 H&H is within a few thou of the case mouth diameter of a 458 WM. This means I can cut 458 WM brass to 1.5 inches, and run them through a .375 H&H sizer to get the correct initial taper to fit the 458x1.5 chamber.