338 Edge Headspace ?

[Highbrass]

From looking at it I would assume a 300 RUM headspace gauge would work for a 338 Edge?
Or would it be a custom ?

 

[tobnpr]

Yes. Necking up doesn't change the shoulder datum length.

 

[sable tireur]

 

[Highbrass]

Now THAT is very useful... Thanks Sable!

 

[tobnpr]

How is it useful?
It's not showing you the shoulder datum, which is unchanged in the Edge at 2.478.
Answer doesn't change, it's the same go gauge as the RUM unless you change the shoulder angle, which is not the case with the Edge. It's nothing more/less than another necked-up (or necked-down) cartridge.