The S variant of the HW100 is the one with a Sporter stock, this stock made from finest walnut and then oiled. It has checkering on the fore end and pistol grip and a nice sharp comb on the stock. The SK has a carbine length barrel, this barrel is 10cm shorter than the S and this can be a real benefit when moving around woodland. It also makes the rifle more compact and this helps shooters keep stable when they are taking both standing and kneeling shots.