Id seperate. Your volume of shooting will be much higher in the AR10 because of the simple fact its a semi auto. Dont ask me how I know that.
My advice? Pick up 500 pieces of whatever quality brass you want for your bolt gun, you just want matching headstamps as it will remove some of the guesswork and variables. I recommend Peterson, Lapua, Starline. Ive used all 3 over the years, and they all work fine. Keep that brass segregate from your AR10 brass, do the normal bump shoulders 2-3 thou and keep shooting it. It will last probably forever unless you get real rowdy with some heavy loads. I do load all my bolt gun 308 on a single stage.
For your AR10? Same deal, but at a larger scale works better Ive found. Pick up a couple thousand pieces of Lake City if you can find it, prep it up, to include annealing, cleaning up the primer flash holes, and the obvious hassle of dealing with MG fired 7.62 with how much work it can be just to get it sized. Once that pain is over, its very serviceable brass in an AR10. One could also just run mixed headstamp if you really dont care, but if you want the best odds of consistent accuracy, a matching headstamp is advised. Even LC made over multiple years is really consistent. I cant say the same about commercial brass from Federal, Winchester, whatever. Commercial stuff simply isnt as tough as the LC stuff because lets face it, semi auto rifles can be really hard on brass. 90% of my AR10 ammo is loaded on a progressive with ball or short cut extruded powders just to make life easy.
If you really are set on dual purpose? Id just go LC or Starline for all of it. Check a few fired pieces of brass, and see what the comparator says for what you need for a shoulder bump, and work from the larger number so it will chamber in either rifle. I generally bump 5 thou for semi auto rifles as they tend to get alot dirtier alot faster, and 2 thou for bolt guns as they stay cleaner.
