The supposed easy button to identify the "newer/better" barrel profile is a serial number starting with 580--- or higher, you will often hear them referred to as "580 series" guns.

Aftermarket support is a bit light for them. Bedding, altering gas port size, accu strut, bolt/recoil buffer are the first pass. You are going to spend a lot of time and some money getting one to shoot MOA, and then when the barrel heats up it may still string them and open up a little.

BUT, i have two of them, shoot them with open sights and realize that with good mags they are reliable shooters that just keep working..... Read this part again GOOD MAGS are important to your enjoyment of the rifle.