Evidently it's possible to glitch or exploit Destiny to load every weapon with nearly infinite ammunition, delivering all of the firepower one could possibly need, and without any pesky reloads either. There are a couple videos of it in action already.
It's hard to tell what work was done to bring this ability to the surface. One video (below) appears to show how the exploit is triggered, but lacking step-by-step instructions it's difficult to tell if it depends on a specific class, weapon, or special ability. It also means we have no way of telling you how to repeat it for yourself. Considering Destiny's heavy multiplayer component, that may be a good thing.
This glitch appears to be the sort of thing Bungie will patch out sooner rather than later, which may be why no one is saying exactly how they pulled it off.