Bullshooter is correct that the washer around the case thing will work with the LCD.

But, not only is the 300WM case longer by the .120 Bullshooter quoted but the shoulder is .1558" further forward on the 300WM case. This means that a .160" thick washer would probably need to be used to get the LCD to work properly.

The custom LCD makes a lot of sense.

The Chosin Few November to December 1950, Korea.
I'm not one of the Chosin Few but no more remarkable group of Americans ever existed.