I was wondering if anyone has ever had to replace an AK gas piston to get a rifle to cycle right? I have an RPK that I recently purchased that the owner had problems with it cycling. The gas piston seem especially loose, so I decided to swap in another carrier to see how it did. It works fine now, and I've ordered a new piston, but I wonder if anyone can measure theirs and give me the size of a correct AK piston.  I'm talking about the diameter of the head of the piston, where it makes the "seal" with the gas block.... I think the worn one was approximately 1mm less in diameter than a "new" Romy AK piston. If I remember correct the good one measured almost 14mm and the worn one was around 13mm.

13.86mm is what my electronic caliper read.  McM

Yeah that'a about what my good one was, I wonder how one wears down by around 1mm?