Before you go loading the same brass to use in each rifle, fire a couple factory rounds through each gun and compare the headspace. If its the same or real close, I doubt you would have any safety issues loading one load for both rifles. However, if there is a .003"+ difference, I would keep the brass separate and size differently also. You will want to bump to bump the shoulder back approx .003", give or take a thousandth. I wouldn't do more than .005" or less than .002" with an auto loader.
Use a powder like Varget or IMR 4064 and work up, starting from around 40gr. You definitely don't want to run into high pressures, that just makes for problems with semi-autos.
As for brass, I use whatever I can but I prefer the thicker stuff for gas guns. I'd get a few hundred rounds of LC brass and start loading.
It's more about residual pressure at the gas port than it is about peak pressure, i.e., the tail end of the time-pressure curve. That's why staying near the 4895 burn rate is important.
