The trigger has to be placed very specifically, or it won't pull the pin far enough or at all. Even if the trigger is pulling the release pin it might not be pulling it correctly or far enough.
That may be the problem but another thing is wrong. The barrels wont rotate at all. Is that because of the pin or something else?
An internal picture of you gun would help. You probably just put some of you internals in the wrong spot (trigger). Also take a look in the internals dictionary.
I looked up the internals before I put it back together and I also think I had the trigger in the right spot, but I'll take another look at it. Thanks