Made a couple mods to the mag release and follower to eliminate the issue of mags not completely releasing. Discovered that when the Rem mag is fully loaded to 15 rounds it will not completely insert lock into position with a chambered round.The Rem mag release slots are .1" higher than the PPQ. This variance places upward pressure on the mag release ears necessitating a slight downward pull on the bottom of the mag to extract it.
I have not been to the range yet.
I wouldn't recommend doing that in this case. Those 4mm mean that with a full mag and a closed slide the top round is forced against the bottom of the breech lug and the mag spring is fully compressed. When you chamber the first round there is sufficient spring space to force the remaining 14 rounds down just enough for the mag to lock correctly.It's not unusual for a full mag to not seat on a closed slide. You simply need to whack it with some authority.
I'm describing only the PPQ 45 when using the Remington rp45 magazine. I believe you are describing conditions using factory mags matched to their respective model.Only if you want +1 (14+1, 15+1, whatever+1). My 15 round PPQ M2 mags all do this in my 4" and 5" (as do my M&Ps, Sigs, HK). Open slide, easy clicks right in. Closed slide, demand respect!
On certain handgun/mag combos, I've seen the pressure exerted by the top round on the stripper interfere with cycling the chambered round. Usually firing the chambered one has enough force to overcome any friction. Hand cycling is a bear.
Now, I don't have a PPQ .45 let alone any Rem mags. There may be issues specific to that combo. My point is that the symptom is pretty common. How someone chooses to address depends on the details. My PPQs are primarily range guns (and amazing at that), so I only load them locked open slide.