GR-3 rifle MK II presentation

an interesting concept you took the Mk1 and scaled it for a Hulk buster sized powered armor. I remember some thing similar in Ghost in the Shell stand alone concept. by scaling up in theory the armor wearer would already instinctual know how to operate the system if they were trained on the mark 1. the Quality of the render and art is excellent but
would nit pick on three points of detail.
1) even scaled for a .50 cal max you can get for a effective range would likely be a mile and area effect may be a mile and a half.

2) a 12 Gauge is fine for close quarters and for a human sized weapon but if your going to go big, might as well go big! a 40mm semi auto grenade launcher, longer range more power and as it looks to me your under barrel is almost already scaled for it

3) the charging handles and selector are on the small size, I think you could ditch the selector or change it to a toggle style and bulk up the charging handles by double after all if the shooter is wearing a powered armor the hand of the armor is going to be big. would also suggest adding a bit more structure to the back of the stock as the weapons bolt needs space to cycle.