I agree w/the gas piston conversation.. to me it's a fix to something that wasn't broken.
There are actually some solid advantages to a piston system for certain applications, like short-barreled (< 16") rifles and suppressed. Dwell times on SBRs are pretty low, and that is not a good thing for a DI system, but is not a problem for piston system. They also tend to work better suppressed as you can adjust the system to compensate for the suppressor or if the weapon gets truly filthy.
If anyone still doesn't think piston ARs aren't every bit as durable and reliable as DI guns, go read a recent torture test by Patrick Sweeney where he does unthinkable things (like literally shoveling dirt directly into the action of a chemically degreased rifle and then firing) to a variety of different piston guns, with two DI guns thrown in as a control group. He was unable to get ANY of the guns to malfunction.
Piston guns are here to stay, and while many still claim "it's a solution to a problem that doesn't exist", I say they are just Luddites and need to accept that ANYTHING can be improved upon, and the piston is a logical evolution of the AR design, IMO.
Look at the venerable 1911 pistol, arguably the best design ever, even it has been tweaked and improved over the years, while still remaining true to JMB's original design. One could say there was nothing wrong with the original design as it certainly worked, but I'll take decent sights, a beavertail grip safety, bigger safety lever etc over the original design any day and twice on Sunday. Same thing goes for ARs.
If you have 4-5 AR's why not build a gas piston version.. but it's more bells and whistles in my book.
Yup... I have two DI ARs now, if I got a third it would it piston one for sure. Well unless it was chambered in .308 then I might reconsider.