I have a Ruger MkII 22/45 that won't fire. When you pull the slide back it sticks without the slide stop and won't even try to close on it's own, also it doesn't cocktail the hammer. It's also hard to get the hinge on the grip to come out to take it apart. I've never messed with any Ruger pistols before so I don't really know what I'm looking at. Anybody got any ideas what might be wrong with it?