Our current Flatwire 17-7 springs for the AR10 are 45 coils.. We have made 42 coils in the past (for Seekins and others)
We dip ours in Sandstom 28-A so they are a grey looking color. (no lubrication needed)
Also keep in mind that while the flatwire is significantly longer in a free length configuration. If you compress both of the above springs to solid height the flatwire will approach 1/2 the height of the round wire. One of the reasons it is a Much better mousetrap..so to speak.