How much ammo does a basic Xcom soldier have in a full magazine/clip? Abilities like Flush and Rapid Fire use 3 and 2 respectively but what is the full size and can it be upgraded? Does shooting always use 1 ammo?
Huwith said it, but here's the detailed answer:
Pistols can be fired infinitely without reloading. Heavy weapons, from the LMG all the way up to the Heavy Plasma, have 3 shots worth of ammunition. This can be upgraded to 6 with the Ammo Conservation upgrade at the Foundry. Shotguns, Sniper Rifles, and Assault Rifles all have 4 shots worth of ammunition, and can be upgraded to 8. The same once again holds for their upgraded versions.
Firing normally always uses 1 shot. Suppression uses 3. Any ability that fires twice uses 2, one per shot. Flush uses 3.