B23
Gold $$ Contributor
For the application you described, it doesn't appear you'll need to mag feed these so why worry about OAL restrictions and mag length. Single feeding your rounds for LR or ELR is pretty normal so I'd probably stretch them out as far as I reasonable could and squeeze ever last bit out of whatever cartridge you decide on. Something off of the WSM case, whether it be 6.5, 7mm, or 30 cal would be my choice.