Having a spare magazine for your pistol when carrying is a must. In the event you have a feeding issue it’s nice to have a spare mag to fall back on. Eject the suspect magazine and insert a fresh mag. A spare mag is also useful for tac reloads on the move if you find yourself in one hell of a gun fight that may require more than 1 mag of ammo. Tac reloads are nice to do during training too if the instructor allows it.
The issue many run into when carrying a spare magazine is the concealment aspect of it. Yes there are many IWB (inside the waistband) mag carriers, but once you have your pistol IWB and possibly a fixed blade knife, the last thing you want is something else inside your waistband. Both IWB and OWB Mag carriers are typically harder to conceal too. They tend to print easier than a pistol.
There is an easy solution to this problem that requires no new gear. It’s called your back pocket. In a recent course I attended with Kyle Defoor, this is how he carried his spare magazine for his Glock 19. It may take you a few days to get used to, but in my opinion it’s easier than carrying on the waistline. Yes a pistol magazine will print a bit inside your back pocket, but the general public won’t even notice (they are too occupied by their smart phones). The only ones who may notice are those of us that carry and are situationally aware.
I have carried in my back pocket wearing both Prana and Kuhl pants with no issues. Both brands of pants work well and have kept the magazine oriented in the correct position without flopping around in the pocket.
If you choose to carry your spare mag in this manner, be sure to train and practice reloads from your back pocket.