I looked this up here on fire
The KS had a cheek piece and round pistol grip knob. The FS had no cheek piece and square knob. The FS was made by Brown Precision and came in camo (pictured a couple of posts above) and in grey.
The FS models had an 18.5 inch barrel with sights. The KS (except for a very few, rare versions) had 20 inch barrels with no sights (except for the 350 Magnum).
There are also differences in barrel taper and contour. The FS has the standard Model Seven contour and was a production rifle. The KS has a slightly heavier-than-standard coutour and came from the custom shop.
M7
