1.Safety setting assemble
2.Stock part assemble
3.Assemble lower box kit.
4.Assemble hop up system.
5.Complete hop up system.
6. Assemble Upper receiver.
7. Assemble Upper and lower receiver then push hammer backward then push auto lever to the front.
8.Tight the screw then complete.
9.Note:
TEST LINK
GHK GBB BOX low temperature test Part 2 - YouTube