For the most part, M1 Carbine sights are 1 click per MOA just like the rest of the "as issued" US Military Rifles. They are really simple but good. My Underwood Carbine is right at 1 click per MOA. Some may be a little off one way or the other. Best way to see is to set a target out at 100 yards and play with the sight to see what your's does.
I'd recommend reading this link for problems with the M1 Carbine sights. But in reality they are pretty simple.
http://www.thecmp.org/pdfs/CC-zeroin...jrearsight.pdf