The Magazine release of TopTech m4's come out just like a real M4 firearm.

Start by pushing the magazine release button into the receiver, so that the catch section on the other side of the gun is protruding as far outward as possible.

Then turn the Magazine catch (the long part sticking out) counter-clockwise wile keeping the button stationary, which will unscrew the button from the catch.

Warning: sometimes the button piece can fly off once unscrewed. Slowly ease off the pressure to prevent losing the button or the spring.