Personaly i dont have an mk , i do won a pm. Kahr says every 3k replace springs , that is fine , i am going on 5k now with no replacement . imho the material of the rod makes no diff .. other than heavyer makes a longer dwell time . imho and without getting into physics of recoil ect.. if you own a short nosed kahr your best off re springing every 5k rounds or so . understand also we are talking about 1 out of 100 or so shooters who will put even 1k thro what is baicly a pocket pistol .