Airsoft guns jam could be caused by lack of maintenance, low of quality of airsoft guns or incorrect usage of BBs or pellets. Components of airsoft gun that often cause the airsoft guns jam are the barrel and the magazine. Lack of maintenance the barrel of airsoft gun cause excessive dirt in the barrel. Dirt in barrel causes airsoft gun jam. Magazine of airsoft gun is the part of airsoft gun that supply airsoft gun with pellets. You have to clean the magazine of airsoft gun from foreign object that caused airsoft guns jam. Read more about How to Clean Airsoft Guns..
Incorrect usage of BBs or pellets can cause airsoft guns jam. Reuse pellets are not recommended because it can leave dirt in barrel. Deform pellets of airsoft gun can cause airsoft gun jam also. When you buy pellets, choose the recommended pellets and high quality pellets to evade airsoft guns jam. Other causes of airsoft guns jam are deformed hop up bucking, damaged nozzle, or damaged tappet plate.

When airsoft guns jam, stop firing immediately to evade a broken gear box or piston of airsoft guns. Fix your airsoft guns jam before continuous firing your airsoft guns. Try to put pellet back into magazine. Use the opposite end of cleaning rod to turn your hop up off and insert that end into the barrel. Force the pellet back into magazine. If your airsoft guns still jam, bring your airsoft guns to your local dealer to be repaired.
In order to prevent your airsoft guns jam, you should read Maintain Airsoft Guns. There are a lot of tips how to evade airsoft guns jam.
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How to Clean Airsoft Guns
Maintain Airsoft Guns