Unless you know for certain how many rounds have been through it, I recommend buying a new genuine Kahr recoil spring.
These small guns are hard on springs and Kahr used to recommend replacement of the K series springs every 1000 rounds or sooner.
Order a new spring direct from Kahr..... DO NOT install any extra-power springs, these mini-guns were designed for a very specific weight spring and anything else often makes trouble.
These K series guns are the Cadillac of the mini-guns.
Shoot it like you would a DA revolver.