Something occurred to me after re-reading this that needs to be added. I reload my own ammo, but haven’t done so in over a year (move and new workshop not completed), which is probably why it slipped my mind. I load ammo at longer OAL when loading for my STI / SV guns.
Also, my 9mm magazines are first Gen SV magazines, not STI. (My .40s are STI).
My point being, and this may apply to newer Gen magazines as well, perhaps we’re seeing the same issues that we’ve seen in single stack 1911s. We’re putting a 9mm cartridge in a .45 frame and magazine. It’s like putting a Subaru STI engine in a 1970 Chevelle.
Another plus to the EDC X9 is the frame and mags are sized to the 9mm.