ok I need help figuring out where to put these vertices(selected) here is the reference, and a few shots of the vertices I need help with.
There are a few picture walkarounds at Prime Portal which should help you out with the shape of the turret. A three quarter view you can find here: http://www.primeportal.net/tanks/marc_peters/m1a1/index.php?Page=1
Alternatively, Gunpoint3D have a free abrams in 3DS that you can download to study the basic shape which seems to taper smoothly from the lower outer turret edge to the turret ring. The only deviation seems to be where the barrel sits, so I would start by doing the tapered undersides first and then cut in the barrel area.