MGS4 - Crying Wolf railgun charging time(?)

[freenutsxd]

Question mark in the title bc I'm pretty sure this is a bug with increased framerate, but I could also just be misremembering how quickly her railgun charges during her fight. See the video below, on Big Boss Hard difficulty (does difficulty reduce her charging time?), her gun charges in less than a second with the FPS cap set at 120.

railgun.mp4