I can do it with my Glock 19 when I want,all I do is turn the gun at a 90 degree angle to the right and slap the mag in.Let me know if it works for you.
BWG 19 I tried your trick this weekened on my G23, if I tap the mag with the weapon at 90 gegrees and slide back it would load on it's own. A first with my 13 round clips