<p>When you screw in a paintball gun tank and there is significant leaking around where you put the tank, the problem invariably comes from a damaged o-ring on the tank. Fix this problem by removing the existing <a href="https://www.thoughtco.com/what-size-of-o-ring-for-paintball-2565851" data-inlink="8qv0eVbdhzqjLHXi53BcYA&#61;&#61;" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">o-ring</a> (size 015) and replace it with a new one.</p>The most common reason for leaking out of the front of the gun below the barrel is a result of a bad o-ring on the front volumizer. This problem is relatively common Spyder-style paintball guns. Simply unscrew the volumizer and replace the o-ring on the volumizer, put a thin layer of oil or grease on the o-ring and then replace the volumizer.<p>When air is leaking down the <a href="https://www.thoughtco.com/paintball-barrel-basics-2565822" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">barrel</a> of a paintball gun the repair is often a little more difficult, though there is a potential short-term fix. You can try to fix it by putting a few drops of oil into the ASA of the gun and then screwing in the tank and see if the problem is fixed, though this fix will typically only last for a short period of time. If the quick fix fails, the problem most likely is caused by a worn cup seal. You must obtain a replacement cup seal for your specific gun and follow the instructions in your gun’s manual to replace it.</p><p>A number of different problems result in a gun not recocking. I recommend addressing this issue by first trying to solve the problem with the simplest solution and building up to more complicated ones. The simplest explanation is that the air tank is empty and you can fix this by replacing it with a filled tank. If that isn’t the problem, make sure that your gun is lean inside and out. If previous paintballs were broken inside the chamber but were not properly cleaned, then the hammer and bolt may be gummed up and can’t slide correctly. You can fix this by cleaning out the chamber and insuring that all the internals are properly lubricated. Guns may also fail to recock because there is indequate pressure on the hammer. You can increase the tension on the hammer (either on the back of guns built like <a href="https://www.thoughtco.com/spyder-victor-paintball-gun-2565709" data-inlink="Y7NohOBJmizK3gcLp6xUQQ&#61;&#61;" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">Spyders</a> or on the side of Tippmanns). If increasing tension still is inadequate. you may need to replace the hammer spring.</p>Double firing happens when you pull the trigger once and the gun fires two or more times before recocking. While this can sometimes happen when the air tank is low, a newly filled tank will take care of that. A more serious problem is when the sear or sear spring is worn out. The sear spring pulls the sear back into place which catches the hammer. When the trigger is pulled the sear releases the hammer, allowing it to move forward and then the sear spring pulls it back into place. You may have to purchase a replacement sear and sear spring and install them by following the instructions in your gun’s manual.Paintballs will roll down the barrel if they are too small for your barrel or if your ball detent is worn out. If you have a large diameter barrel and small diameter paintballs, they may roll down. More commonly, the ball detent is worn out and must be replaced. This can be done by following the instructions unique to the model of your gun.