I got one last year to test it out. Mine was the Kel-Tec SU-16A. As a test I also got a case of Wolf 62 grain FMJ. I shot the whloe case off it three visits to the range without a single problem. These are reasonably accurate rifles but as the barrel gets hot groups start ot open up. The shorter version barrels are a bit thicker and more consistant.
I did not have problems with any mags. The plastic mags that come with it have given some people trouble, but if you ave problems with them Ke-Tec will replace them without any hassles. My mags that came with the rifle have worked fine. The Kel-Tec mags will not work in any other rifle but any Ar mag will work fin in theirs. They have great customer service.
Once you learn how to disassemble it it cleans up easy, and the bolt stays clean as it uses an op-rod instead of gasses to cycle the action. Being able to carry the two included ten round mags or one 20 o 30 round mag in the stock is handy. They fold up into a nice compact package that makes it easy to keep them out of site.
It's no AR or Mini-14, but they work as advertized. One one of the sites dedicated to these rifes, one guy did a heck of a torture test in the middle of winter at his range. He shot a couple hundred reounds to really heat up the barrel and then broke through some ice and threw the rifle into the water to cool it off. Retrieved it, drained the water from the barrel and kept on going. Rifle maintained it's point of aim and onl problem he had with it was a defective casing not ejecting properly.
Sometimes I put a T168 scope on mine for fun. Works fine. I also got the adjustable rear sights from Kel-Tec. These are standard on some of their models, but mine is one of their early models. I used to be a Q.A. Engineer and these litlle rifles always intrigued me so I got one to put it through it's paces and it has performed fine.