I shoot Georgia Arms 55 grain FMJ (bought 1,000 rounds at the gun show) and get better groupings. I can't provide measurements though. Like you I'm using an EOTech sight. There's no way I can be certain that I'm holding at the same spot for each shot, its always a best guess.

As someone already suggested, try putting a scope on it and then try out some different ammo. I'm about ready to move a Leupold 4x12 off of another rifle for a few months just for the heck of it. The EOTechs are fun but as they're intended for close quarters I mostly practice for decent off-hand groups at 50 yards.