Started with a standard Bushmaster A2 Carbine (16" heavy barrel) that I bought 10 years ago...but hardly shot. I wanted to turn it into a varmint rifle and start shooting it more so I put on a flat top receiver, free floating tube, Vortex scope, and adjustable gas block - all else is stock. I was very disappointed today when I turned in 2" - 3" groups at 100 yds. I was shooting PMC factory ammo - 55gr. FMJ BT. I was hoping that this rifle would shoot something close to moa (understanding that I might not quite get there with non-match ammo and a standard chrome-lined barrel). Maybe that was too much to hope for, but 2-3 moa...really? What advice can you give to get me down into the moa region?