I did a lot of research about the gas piston. Being an arms dealer, I have specialized in exotics for some time now. The gas impingement system isnt bad as long as the parts in the upper are kept relatively clean and lots of oil is used. The blowback fouls up everything in the upper and it builds up relatively fast and creates issues and can lead to jams. When oiled and maintained, its a pretty good system and is reliable. If the point of the rifle is to be used non stop, very little cleaning and basically ignored, then piston is the way to go. I converted almost all of my AR carbines to the Bushy piston system. What little oil I use on the bolt is still there after firing 100 rounds and the bolt/carrier is cool to the touch. Reliability seems to be 100% so far, but keep in mind, a well cared for gas impinge system is also (it just needs maintained). The best conversion system will be one that replaces the carrier, not just replace the stake key (the hole tube on top of the carrier). This is an area of major impact and they could break after time. The Bushy is all one piece, but this also keeps the price kind of up there...$400. This does make for a great SHTF kind of gun as it needs nothing, just ammo. The AK is still more reliable (not enough time to explain) but there are many short falls of the AK, better off with an AR piston. There are some other really good piston ARs, just do your research. Keep in mind that Bushy does sell a complete piston rifle. AND, this complete rife piston is a little different than the conversion kit that they sell. The conversion kit is a modified ARES system that had the bugs worked out and I'm convinced that it is really good. Good luck.
thanks for the info I was interested also.