so I just got this air gun and I was trying to put the co2 cartridge in the gun, I saw some videos saying how you just screw the bottom in real fast and hard. but even when I screwed it all the way the leaking still went on. I later realized that there was co2 coming out of the gun barrel. this is my first time owning an air gun and I don't know whats causing it. is this possible to fix? the gun and the co2 cartridge are both made by the same company umarex and the gun is beretta elite II. tank u and have a nice day (sorry for my bad English)