Air Force Texan Guys!!

I can't help a lot but can give a little advice anyway, my .45 was stock and I would shoot it off a 3000 psi tank tethered and yes it would shoot very consistent I was tethered to a guppy bottle so I could go through a lot of shots before I noticed any fall off I had another full size 4500 psi tank that I would Jack back into the guppy to run it back up to 3000 psi.
It needs to be noted though that the .308 uses a different valve and set up than the .357 and .45 so I don't know 100% though 

Also as far as I am aware the Texan SS only comes in the .45 right now 
 
Explore some more before you commit to the AF .308...
it can be very hard to achieve accuracy in that model Air Force for some unknown problem.
I have a awesome .457 Texan and a friend has a great .357 so we like Air Force, just not their .308.

But it's not the caliber, there are some tack driving .30's out there, both pellets and the lighter range bullets from stock guns and conversions.
Know a guy with a .308 Marauder bottle gun w/ Cobra valve that gets five shot 1.4 groups all day long at 100 yards (and that is WITH the flyer!, 3/4 is not unusual) but he's got $1100.00 in the rifle