Tactical reload
What is a tactical Reload?
A tactical reload is the action of reloading a weapon that has only fired a few rounds out of its magazine, and retaining the round in the original clip. The best example is an infantryman reloading before entering a hostile building, but is concerned about ammo. Conventional military wisdom states that you should always have a full magazine before entering the building, but the infantryman cannot afford to lose the ammo.
Therefore, he executes a tactical reload. He ejects the magazine with the hand holding the weapon while drawing a new magazine from his person. Before the used magazine drops out, he catches is with his other hand (the one with the fresh magazine) using his fourth and fifth finger, and inserts the fresh magazine with his thumb and index finger. This way, if he runs out of rounds later on in the fight and is desperate, he can use the slightly-spent magazine he retained.
Advantages and Disadvantages:
As stated in the previous paragraphs, the main advantage of performing a tactical relaod as opposed to a speed reload is retaining the extra rounds for future use. The main disadvantage is that tactical reloads take longer then speed reloads if you are not experienced with them, and leave you with no defence if the weapon is open bolt.