Don't listen to others - Adams Arms P Series Micro Block Pistol Length Piston Kit

This is my second AA piston system I've upgraded to. To me, not have to clean out the chamber, bolt carrier and bolt are a win for me. You still want to run with lubricant, but these systems run extremely well and very clean. I highly recommend them if you have patience or have them installed by a gunsmith. The hardest part is finding a barrel nut that works with a piston. On top of that, finding a handguard that works with said barrel nut. I recommend a standard GI barrel nut and a Samson Evo style handguard to save you the trouble. After said and done you will be impressed.