Okay so each frame is 96x96 in size, (a large buffer window since i'm not rendering large weapons) They are all centred at the bottom of this graphic like so. The hitboxes are like so:
Idle:
Falling:
The head positions are a little different however the base hitbox is always the bottom of the graphic. (The 96th pixel)
Edit: Just realised I messed up the cropping of the 1st image at the top, my bad.