I prefer that my students retract/lock the slide first, then insert the magazine. The reason is that a full mag MAY be difficult to seat and LOCK in; potentially causing an operator-induced failure to load (chamber).
Also, inserting the mag first, then manually retracting the slide MAY cause a failure to fully go into battery (slide fully closed on a chambered round) IF the operator rides the slide forward rather than letting it close under full recoil/operating spring pressure.
If your pistol does NOT have a slide lock (many older, smaller guns) then you must follow the order you describe. Most modern combat pistols do not fit this parameter.
If you must do this task in inverted manner, I recommend you grasp the slide firmly with the support hand, pinky forward, fingers over the slide, thumb along side away from the hammer or wrapped around the rear of the slide (hammerless/striker fired) and pull the slide briskly rearward toward your firing shoulder, allowing the slide to be pulled from your grasp when it reaches full retraction, thus allowing the recoil/operating spring to get “a full head of steam” to strip, feed and lock on a round.
Hope that helps.
God Bless & MOLN LABE
Thank you for the info.
/I love the wealth of knowledge we have here in Freeper land.