In really intense battles, you can save the bullets too realease at just the time you really need them. Like when the almost dead opponent is running away, or when your shotgun runs out of ammo. The pistol becomes a sort of complemetary weapon too the bigger guns, and doesn´t need reloading so much if you only use it when it´s undoubtably the best choice.
Maybe some way of more actively reloading it would be nice though. Like reloading faster if you stand completely still, isn´t shooting and isn´t hit by anything for example, so that you can take some temporal cover and reload in ammo-shortage situations. If som kind of animation and/or sound made it clear that you go into fast reloading mode I think such a system could be quite intuitive.