Circuit, being a unicorn with only the two spells of advanced levitation and precision electrical manipulation, does not have a force field spell. She instead creates the illusion of a force field by combining the two spells she does know. By creating a totally permeable barrier of feedback-giving electricity (allowing her to essentially “feel” anything which passes through it), she senses exactly where every object is that comes into contact with the field is. She then levitates that object away with double the opposite velocity it entered with. This is very taxing on her brain and becomes near-impossible to hold together when performing this combo spell while being berraged by more than 100 projextiles a second in more than a one direction. It also makes it exrtremely difficult to do anything else at the same time(especially walking). Essentially, this spell is only useful under certain circumstances. Because the bubble is based on speed of rapid fire and area of attack; the speed, size, and power of the projectile don’t really matter. Which makes this spell perfect against slow but high-magnitude attacks such as magnums, snipers, grenades, and rockets. Assuming such weapons are being fired one at a time.
 
Basically: Widowmaker can suck it.