I bought mine used from a guy and couldn't get the disconnect to work properly once I put the upper on. It wouldn't catch if I was holding the trigger back. This is big time no-no. Jard told me to send it back for a replacement even though I didn't buy it from them and they had no responsibility to help at all. It may have been the trigger, but it may also be the lower receiver. I have other problems with it, like the mag well is a little undersize and I have to force the mag in. I am sending that back, too. Customer service at Jard is outstanding. If the trigger is anywhere near as good, once I get it back, I know I will be happy.
Fast Ed