Hop up

Hi everyone. Now being an owner of the galaxy mp5 PDW, i'm pretty happy.. except one thing. About every mag i shoot, i have to open up the handguard and adjust the hopup. For some reason it is sliding back in the gun automatically when i fire the weapon. This causes my shots to be very inaccurate after a while because the bbs go just about straight up. Is there something wrong with the hopup or do I just have to deal with this?

Well it is most likely being caused by the vibrations from firing. I'd recommend either reinstalling the hopup or using tape to hold it in place.

The vibrations are causing the problems with with your Hop-Up, there are a couple of ways to correct this,

The easiest being tightening the screw on the adjustment lever, or placing a small rubber washer under the screw.

Another is using a small amount of Shoe Glue, just a drop, shoe glue when it dries stays pliable, and can be removed later with just a fingernail. When you have your Hop-Up adjusted to just the way you want it, apply a Drop of Shoe Glue to the Adjustment lever, let it dry, and the gun should hold its setting for about...... Until you Remove the Glue.