I have a KS-5 Special that I have shot for 12 years. Bought it used from Joel Etchen. Had it rebuilt 3 years ago. I don't think it was ever rebuilt before I owned it because the receiver face was not machined. So I shot it for nine years without a service. Not recommended, but I did it. The locking lever started locking up tight. Could not open the gun once every 100 shots, without putting pressure on the top of the receiver. Four moving parts inside. When you move the locking lever you cock the gun. Fewer springs and parts to wear out. Simple but very effective. The only difference between the KX-5, and KS-5 is the KX-5 has an adjustable trigger (LOP), and the push-button forend release.
The gun does seem to kick with 3 dram loads but can be cured with some barrel work (backboring). I also put an 11 oz. recoil reducer in the butt stock. I am also 6'1" and 250 lbs. of which was mostly muscle back when I bought the gun but has since changed a bit. LOL. Pricing, KX-5 $3500, KS-5 Special $2700, would be a good buy. Good time to buy a used gun not only because of the season, but the economy really nocked down the pricing.