Barrel contour and cartridge help

[long-gun 308]

I'm in the process of starting an ELR build and I'm unsure of barrel contour? Heavy Palma or MTU? Or any recommendations on contour. I'm looking to get a finished length at 30 to 31 inches. For cartridges I'm looking at 30 Sherman magnum or 300 Norman mag. I'm not sure I want to jump into anything over a 338 mag for my first build.

 

[Taylorbok]

As big as you can fit. Straight 1.25" if possible.

 

[K.E.C.]

Howdy, I went with 1.25 to 7/8. 30" long. As far as caliber, what brass can you get or have. Also had the barrel fluted.