Welcome Praelus,
You pose a good question.
I have had my R9 for quite some time, and usually do not always even carry a spare mag any more.
I do practice reloads at the range, and for me they are quite un-tactical in nature.
It goes as follows:
Switch the emptied firearm to my off hand, flipping it upside down with the muzzle facing down range, pressing down on the magazine floor plate with my off hand thumb, pry back the heel release with strong hand thumb, and pull the spent magazine with my strong hand.
I then have to pull the fresh magazine from my off hand front pocket, pull it from its pouch, push it into the mag-well, flip the firearm back to strong hand firing grip, slingshot the slide, and now i'm ready to go.
All this may only take 5 seconds,and can be done without looking, but it could be a literal lifetime under the wrong circumstances.
I hope this helps.