Re: 338 Edge seating depth: how deep is too deep?
When you seat a VERY long bullet like the 300 Berger that deep you are certainly reducing the case capacity jamming the bullet so far down in there. When case capacity is reduced, pressure rises. I don't know how much velocity you would be giving up over a longer seated bullet, but it would be some for sure.
If you are not worried about the velocity loss, I can't think of anything else that would be problem.
There are probably others who can answer "how much" better than I can. Obviously, if you have access to a 338 Edge a little experimentation would be fun and informative.....