I have never owned a piston type AR and was pleasantly surprised at how clean the SR556 was after firing the first120 rds through it recently.

I expected much more grime than I found, especially near the bolt and chamber. I did note that the area near the gas block and muzzle was a bit dirtier than I've experienced in the past.

It sure saved some scrubbing in some hard to reach places! ;)

The firearm performed flawlessly with the exception of some Independence 5.56 XM193 rounds. The primers kept popping out every 3 - 4 rounds, requiring that I safe the weapon, remove the mag, clear the weapon and fish out a few primer pieces before continuing. I set that stuff aside and moved on to some WWB M855 "Target", some PMC XTAC XM193 and some American Eagle XM193. All those brands fired just fine.

I did not tab the ammo's performance as it was a brand new unit just out of the box, with a few enhancements, so I figured I'll fire it a bit more to see if the groups become smaller over the next 100 - 150 rds. The best group of the day, just a bit over 1.25" @ 100 yds, came with the M855 spec'd WWB. Once I'm certain it is consistent, I'll start documenting different load performance.

All in all, it was a good first outing!

MOA of 1.25 is pretty good for a first outing. As for bring cleaner. Piston guns just get dirty in a different place. It does make for a quicker clean up usually.

That is similar to what I have experienced with my SR-556.  Sometimes you have to tweak the rifle with the gas adjustment.  I found running Federal XM-193 on a gas setting of "1" tighten up groups considerably down to about 1" at 100 yards.  They are great rifles, easy to keep clean and fun to shoot.  Melvin Johnson has thousands of rounds through his with no cleaning of the piston and it is apparently still running trouble free.  Haven't seen a round count lately, so he could be past 10,000 rounds.

Just now reached 10,000 rounds.  Please see here for info.

120 rounds? hell a DI gun is still clean after 120 rounds. try 1000 and let us know what ya think. thats the benefit of pistons, far cleaner over the long run.

as for indy 556 ammo, some of the older lots were loaded too hot. i had really flat primers and increased recoil in DI uppers. so i wouldnt blame your rifle.

are those ruger barrels chrome lined or nitrided? with accuracy like that i'd guess its not chrome. my nitrided LWRC upper is more accurate than my chrome lined barrels too.