There are several scrolls, affixes, etc that effect ammo. Many put ammo in the magazine, one completely circumvents the mag entirely (probably that one, it's called advanced depot), and so on. Often it's several things in conjunction that let you keep firing till the bipedal, gunslinging cows come home.

Hi guys,

Just got this game a couple days ago and been loving it. 
I cant figure out how some people use concealed ammos skill ability non stop.
Is it a talent or inscription that allows them to continually refill their ammo?

Concealed ammos skill reload?