The Kel Tec PF9 is the lightest and thinnest 9mm available. Take it apart and the slide weight and barrel weight are noticeably less than similar Polymer frame subcompact 9mm pistols like the Ruger LC9 for example. One problem of building the slide so light is the higher possibility of failure. The PF9 has a history of slides cracking.
I noticed a hairline crack in the slide where the slide stop engages. The crack goes all the way through. The crack is visible on both the inside and outside of the slide.
I shot the gun again today but didn’t notice any increase in the crack size.
I’ll contact Kel Tec customer service and make arrangements to get it repaired. One good feature of owning a Kel Tec is the lifetime warranty for the original owner.