I owned a Kel-Tec .223. I think it was a SU-16(?). The folding stock .223 that does not fire with the stock folded. I found it to be wildly inaccurate. The problem seems to be that the barrel is not supported well. If I changed my "hold" the point of aim and point of impact would deviate by more than 5" at 100 yds. If I used the bi-pod, the POI/POA shifted by at least 2" in a random way.
I also found the penetration ability of the .223 to be lacking. Sold the Kel-Tec and bought a Siga 762x39. Much better rifle, cheaper and more reliable. Much heavier though. Suits my needs well.
I strongly suggest you shoot the kel-tec before you buy.
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...........From Nomad.........Been "on the road" since '97