A sincere question on these two steps:
“Step Two- Retract and lock back the slide by drawing the slide rearwards with your support hand while depressing (of lifting) the slide lock.
“Step Three-Insert a loaded magazine with your support hand, guiding the magazine into the well with your support hand index finger; firmly seat the magazine by slapping or pressing upwards on the bottom of the magazine with the heel of your support hand.”
I know that functionally these two steps can be performed in the opposite order (i.e., seat mag, pul slide back fully and then release to fly forward, chambering a round). In fact, it is how I have been taught, inc. in a NRA approved CCW cert. course. Is there a safety reason why they should not be?
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