Given how conventional firearms work for Homura, I'd say that it would result in the laser pulse leaving the weapon then freezing in mid-air after a certain distance from her or the target. However, due to lasers being invisible IRL, she would see absolutely nothing happening other than the battery losing power if we were doing this without Fallout's mildly cartoonish stuff. Then the target would explode with all of the lasers hitting within microseconds of eachother, giving a perfect opportunity for the obligatory post-apocalyptic reference.

(Disclaimer on lasers being invisible: Technically a laser weapon would give the visible pewpew if it were powerful enough, but it'd have to be ridiculously powerful to the point of dwarfing most Fallout laser weapons. The resulting visibility would mostly be the air turning into plasma, though, and not as much light leaving the beam.)

Hope, Hope never changes