If you're having problems adjusting your KWA LM4 Gas Blowback Rifle and afraid that you might damage a US$300++ airsoft gun, better read this advisory issue by Airsoft GI which they posted at their Facebook Page... "Heads up all you KWA LM4 owners! To adjust your hop up correctly without damaging your hop up unit follow this procedure:

1. Ensure your rifle is safe and clear.
2. Split open the receiver by punching out the rear body pin.
3. Remove the bolt and charging handle.
4. Proceed to adjust your hop up using the provided hop up key with a little downward pressure directly on top of the hop up unit ensuring that the key and hop up unit mesh properly.
5. Make very small adjustments.
6. Reassemble and test fire. Repeat procedure as needed."

If that's still difficult for you and prefer a more visual way, they promise a video will be uploaded soon to explain this more in-depth.