How about slide velocity. Is the Gen4 23 bouncing cases off the ejector at a faster velocity. In the video the recoil of the 17 does not look as forceful.
Glock went to the Gen4's in .40 first and they work. I often wonder if they should have upgraded the Gen4 9mm's with a frame and magazine release only and left the 9mm top ends the same. My argument is flawed because some Gen3 9mm's are having the same btf issue.
Sometimes new isn't better.
Good report and video as usual.