I have a G&G MP5 Blowback. 1- Remove the bottom rail 2- split the handguard in 2. 3- You gotta split the nunchuck and put 1 part of it each side of the barrel. 4- reassemble the handguard 1 part at a time. Watch not to damage any wire.
(me english bad) . the whole process takes a big 2 min when you are used to it.