new to airguns,I am already going down the rabbit hole have an hw95 Lexus and a Gamo coyote.I’m going to cool it for a while till I can get an accurate pcp. My problem is I am trying to fix a hatsan at-45l .it leaks .do I need to use seals made for this rifle or will generic seals,this is for my brother in law.or would he be better off buying a urmarex.