Re: 338 lapua and 458 win mag
338 Lapua requires a magnum length action (3.6")
458 WM requires a standard length (30-06) action (3.34")
Not all manufacturers differentiate between these two lengths. Remington long action for instance is 3.6". I think, but am not sure, winchester makes a 3.34" action. Therefore, it will depend on your action.
The bolt face is a different size between the two rounds, so you would need to get a new bolt or pay a gunsmith to modify.
