I got some cheap Russian 9mm, and my PF9 refused to feed it, but my Hi Point carbines, Ruger PC9, Taurus PT111 and S&W Sigma handled it just fine.
Then I got some Wolf (also Russian), and while the Kel Tec will feed it, the primers are almost too hard or something because I get about half that won't fire, but do fine in other guns. My PT111 does OK with the Wolf with one minor problem. They tend to hang up on the mag when I'm loading, like one down towards the bottom of the mag is wedged and the spring pressure isn't there to hold the top few rounds in the mag unless I thump it a couple times.
I guess it depends on the gun.
My Hi Points, Rugers, Sigma will eat anything I put in there.
I also had issues with some .380 Hungarian ammo in a Kel Tec not firing.
My Bersa Thunder shoots it fine.
I think Kel Tecs don't strike very hard.