I have a Les Baer .308 Semi-Auto Sniper,
The rifle has a 20-inch, Les Baer heavy weight barrel with the Enforcer muzzle brake.
The gun, weighs 11 pounds. With a 3.8 - 22X U.S. Optics scope - right at 13 pounds - not hardly handy for a day walking in the field shooting game - but it is damn accurate from a bench to 1,000 yards.
It will shoot 0.375 10-shot groups at 100 yards using Federal Premium Gold Medal Match ammunition. This ammunition uses a Sierra 168 grain boat tail bullet at 2650 feet-per-second. I have tested this on two occasions in a 100 yard tunnel with repeatable results. The gun was shot from sand bags and the top of the barrel sand bagged to help keep it steady during aiming.
Here are some observations on .308 AR's in my long range usage over the past two years. Bullet concentricity related to the case central axis can kill accuracy. I test every round with a concentricity gage to verify that they are with 0.0005 of zero deviation - or they become short range ammunition.
You will never shoot enough .308 in one day to make a difference in how clean the gun runs between a DI or piston gun - at least if what you're shooting is for long range accuracy. Heat is the enemy and you need to let the barrel cool to some extent or, once again, you start losing accuracy. This alone will limit the amount of rounds you will run in one session. It's not like an AR15 where you can easily go through 500-1,000 rounds. If you shoot 200 in one session, believe me - that's a lot.
The Les Baer bolt + carrier are NP3 coated. I just take them out and wipe them off with a cloth, oil lightly, wipe out the interior of the receiver and reassemble - the rifle just doesn't get all that dirty like an AR15. In an AR10 - the piston VS DI operation debate is nonsensical for long range rifle use - it really doesn't matter - and, for reference I run a Barrett REC7 AR15 - so I have a piston rifle.
Wind drift between the gun location and target location is the biggest problem to overcome. Get a notebook and a hand held anemometer - take copious notes every time you shoot. The more "dope" you have on how the gun shoots - the more repeatable the results.
I've been able to hit an 18-inch steel torso target repeatedly at 960 yards in a variable 9-15 mph cross wind by very carefully observing the conditions and waiting for the breeze to drop across the entire distance - and then using the horizontal compensation required on the Mil reticle for a 10mph wind from my notes. If you don't keep shooting notes - forget it.
Have fun with your new rifle!