It's hard to figure if you already build the rifles but it sound like since you mention both are 9.5lbs etc only difference being the chambers. If not.
Couple thing I always look at building, what bullets I want to use next barrel twist/length plus having a magazine length for them also how there throated.
As you said "I was think over 500, probably closer to 800 and work my way out"
also "but would like to have the option to hunt with it as well."
I've got a nice 270 that I had build as a hunting rifle also couple 30-06 and I could use one with some of Berger target bullets if I wanted. If I was looking more at the 270 also to include LR target shooting I would of build it more to handle the Matrix bullets in 165gr and 175gr bullets.
Lot of choice building.