Re: 338 EDGE
The 300 Tomahawk usually nets around 115.5 of water, that is exactly what the one I built holds. Can vary a small bit 115~116. I think the biggest benefit is the brass is chaper and no need to open a bolt face when necking down the Lapua case.
It's not to say that the Lapua case is worse than the 300 rum just that brass is a lot chaper. The Lapua brass of course cannot be matched for consistancy or quality when compared to Rem or Fed brass.
I suspect that the 338 Tomahawk will have the same net results if nothing other than the neck diameter has changed dimensions. The 338 Tomahawk parent case is the 300 rum case.
One other note of interest, these guns with huge case capacity while out beating there rivals in factory barrel lengths by a few hunder feet per second, they really exceed when longer barrels are used especially when going beyond 34 inches. This also allows the user to use extremely slow burning powder to acheive maximum velocities with less throat errosion.
In the 300 Tomahawk I built; we managed to launch the Berger 190 at 3600 fps behind 100 grains of H1000, and the Berger 210 at 3300 with same amount, when using the same amount of H50BMG we dropped to 3100 on the 210's and never bothered with the 190's as 3600 fps produced fantasic groups and long range accuracy. This rifle sports a 34 in Lilja 1:10 twist barrel accounting I'm sure for higher velocities.
As always work your loads up and do not attempt to laod at MY loadings in your rifle.