I don't think it's overpowered. It might be teetering on the edge a little bit, but as it stands right now, it's fine in my opinion. The charge time is long enough and the charged shot takes up half a clip, not to mention that the shot only goes slightly past melee range.
I think that as the shield and other stats stay right now, the boltshot is fine, but if some of that changes, the boltshot might become a little bit out of balance.