I bought one of the original Cobray M-10's, chambered for the .45 ACK, which fired from the open bolt. It was merely a "fun gun" for awhile... until it started going full-auto when least expected! The problem was with the heat-treatment of the semi-auto disconnect. I replaced the worn parts, but still didn't trust it. Besides, accuracy was NIL! Fortunately, someone wanted to buy it, or trade for something else. I got a NIB Colt CAR-15 (at the time, $400 was the "going price" for the Colt CAR-15) in the trade.
Several years later, supposedly after the problem with incorrect heat-treatment of parts was solved, I bought a Cobray M-11/9. Accuracy was still NIL, but I sort of expected that. The modifications that Cobray made to the original version of the M-11 (without the "/9") made it HORRIBLE! LOTS of trigger lash....to the point of being painful after firing only a few rounds! Cobray started selling a trigger group kit that supposedly solved the trigger lash problem, and I bought one. It did solve the problem, somewhat, but not to my total satisfaction.
Would I buy another one? HeQQ no! While it feeds just about anything, the accuracy of it sucks. The phospate finish tends to suck in moisture, and having surface rust appear after having handled it dry is a MAJOR problem.