the difference between the DM4 and Proto is...
On the proto, they got rid of the On/off thing under the barrel of the DM4, and moved the LPR to the front
The proto's bolt is shorter, and can be run at a higher PSI for better gas effiency
The proto has Push buttons in the back like an angel instead of a membrane
The proto has a 1 peice eye cover that goes over the top of the body
the proto has a non/clamping no rise feed neck
the proto comes w/ the proto barrel (which is equilient to the dye excel barrel) instead of the ultralight the DM4 comes w/