As for the first situation you describe, it may happen (not so sure, however) you see it, but for two separate causes.
For example, in turn one you may fire a long burst against an opponent 3 hexes away, with deflection etc, so that your final fire value will be zero; anyway, you have fired, the result of the shot is a zero value AND you can find your guns jammed after the shot.
Note that when you don't fire because of jamming, it is pointed out in the shot line (it will end with a "jammed" notice), which is different from a "normal" zero value shot.