Currently (as of 2025-10-03), this article describes "long-stroke gas piston" as having a piston that moves more than one piston-diameter backward under "high pressure". It defines "short-stroke" as moving less than one diameter under pressure, and says it is still short-stroke even if the piston travels several inches further, perhaps attached to the bolt itself. Both of these "definitions" are not cited and are flagged as lacking citations.
The idea that the short- vs. long-stroke distinction has anything to do with the diameter of the gas piston seems entirely alien to me, I have never read or heard that anywhere else. The idea that it has to do with distance traveled under high pressure, and thus the location of vent holes, also seems fairly weird.
Based mostly on C&Rsenal Youtube videos and written sources recommended by them, including on the M1918 BAR and the Russian SKS, I have gotten the impression that short- vs. long-stroke is very analogous to short- vs. long-recoil action, where "long" means that the piston (or barrel) travels the entire "action length", or the length traveled by the bolt face or bolt carrier, whatever reciprocates the longest distance. "Short" generally means the piston (or barrel) travels less than the full action length. This would make short-recoil and short-stroke quite strongly analogous, with one describing barrel recoil and the other describing piston movement. I have never seen piston diameter mentioned, and that would feel arbitrary and not particularly relevant to the mechanism.
However, I am not the right person to find a source about firearms design terminology in general. Fluoborate (talk) 13:48, 3 October 2025 (UTC)