I just put a short piece of brass tubing over the pin to make it a slight bit larger haven't shot it yet but the barrel slop is gone I'm thinking it should be good. Not sure when I will get out to shoot it, always had to make sure the barrel was up all the way when I shot before this will be better and more enjoyable to shoot now.
I am pretty sure Gamo has taken to pinning them for a little bit now. Even their top end BSA Lightning is probably pinned, according to reviews at least. Such a pity, could have been such a nice rifle. I don't know about the Hunter Extreme or the Gamo Magnum, but if I were to guess, I'd bet the extreme is the only Gamo rifle with a bolt through the pivot these days. I do like the brass tubing fix, and I still like Gamo's bottom end rifles. They represent a great value and they are light and generally accurate enough for small game. I just wouldn't expect them to kill pigs...