Not just discarded.

In Borderlands 2, most Tediore guns are so badly made that after you finish off a clip of ammunition you have to throw them away before they explode.

Tediore decided that this would be a feature, and made the ammunition supply unstable to the point that the gun exploding also cooks off all the ammo, making the explosion bigger. I have killed myself accidentally by manually reloading one of these guns between fights.