Tracking individual shots isn’t really that fun. That’s why Future Fantasy introduces the Ammo Factor for most ranged weapons (and some melee weapons!).
Ammo Factor is a number from 1-20, but usually near the lower end of that. When you make an attack with a weapon with an Ammo Factor and the unmodified attack roll is equal or less than the Ammo Factor, you’ll have to reload after the attack is finished. Whether reloading is a move or a minor action depends on the weapon.
Weapons with a large clip size usually have an ammo factor of 1. A weapon with a smaller capacity, like a six-shooter, would have an ammo factor of 3. A pump action shotgun, which needs to be reloaded often, might have an ammo factor as high as 7 or even 10. A missile launcher, which needs to be reloaded after every shot, has an ammo factor of 20.
Some Soldier abilities might let you lower your ammo factor. Some Tactician abilities might lower the ammo factor of your allies. If you have to make multiple attacks with a single action, and fail the first ammo check, you still get to make the other attacks- you aren’t out of ammo until the end of the action.
What happens if you’ve got a 2-shot capacity shot gun and manage to keep making your checks? Clearly you were reloading during the enemy’s turn when you saw an opening. What happens if you fail your check turn after turn on your gun with a huge magazine? Either you’re wasting lots and lots of shots with burst fire, or you’ve got some dud clips.
This also opens for special ammunition one-shot items- use the clip, and you get the benefits (like heat seeking bullets, tracer rounds, or exploding bullets) until your clip runs out.