Re: 300 jazz
Thats alot of questions.
The 300 JAZZ case capacity I would guess is slightly less than the 30-338 Lapua, as the 338 Norma is slightly less than the 338 Lapua.
Barrel length on my rifle was 28". I sold the rifle last year after shoulder surgury, along with all of my big caliber rifles.
However, if memory serves, the 210Berger's were going 3150, and the 240gr SMK was 2950-3000fps. I could have pushed it harder, but as it was a new wildcat, I stayed on the safe side. Accuracy was exceptional, and ES was single digits.
The 300 JAZZ alows you to use these bullets in a standard magbox, and be able to load with the base of the bullet seated at the neck shoulder junction, and avoid donuts. The 30-338 Lapua does not.
SSG built the rifle, give Nate a call and discuss a build.