I had the opportunity to fire a piston AR about a month ago. I put about 3 mags or so through it. I was shooting cheap ammo-whitbox stuff. Using Pmags (illegal in MA, but I was shooting a buddies rifle, up in NH, where they arent). My opinion? I didnt like it. There were feed issues. I had no issues firing the same ammo through mine-through the piston AR, I would often get double feeds, and FTEs. I had to push the brass out using a barrel cleaning rod a couple of times. I used the same setup on my AR, and experienced to issues at all. I did like the less felt recoil of it, but, the FTF/FTE issues, turned me off.