I think its called an LPR cap(but no lpr on it), the thing directly under the barrel. But, i didnt know you had to put it on tight. So it was leaking like crazy and i havent used it much(twice). But the former owner came and fixed it during a game.
My question is, is it ok to have the oring stick out a little bit? Because i try making it so none is sticking out when i tighten it, but it squezes out
the reason it's sticking out is because you didn't put any lube on it. you should put lube on any o-ring that is on a part that screws into another including a barrel o-ring imo. it helps seal it and prevents tearing.