seems loose, but I noticed that the older Pmag has a lighter spring than the newer gen3 20 rd pmag. If I insert an empty mag, the bolt catch actually depresses the follower a bit. There is a shiny spot on the top of the catch, so I am assuming the bolt is scraping past it on the last round
If you want to try that, I suggest you get a couple spares and use the shank of a small drill bit to test instead of putting the roll pin in and out several times.
One thing that might happen some times is a hydrolock on the BHO plunger hole if the fit is tight and you get some lube or water in there. If that is happening, you might try cutting a tiny groove in the hole top to bottom to create a pressure relief, just be sure to deburr it so things move smoothly.
I had the same issues with all my EARLIER GENERATION 20 rd pmags. 30 rders have no problems. I have a total of ONE newer generation 20 rd pmag and it does not exhibit this problem. I just stopped expecting flawless performance from the 20 rd mags and moved on.
Any more info besides "20 rd pmags"? You sure its a magazine issue? How about worn rifle parts causing "short-stroking"? Have you tried a NEW "pmag"? And are they really "pmags" or just "polymer" magazines?