Mine is definitely not locked because when I try to lock the mag in the gun with the little rocker clip, the clip wants to push the extension off. I can make it lock by using two hands but I can still push the extension off from the rear, if I try. In use, of course, the force is from the front on the extension so the gun should shoot fine with it as.
I wish there were a way to secure this with a screw. Being able to change clips in a hurry and without having the clip come apart is important.