M4S-System Disassembly Guide Part 2
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Heres how to get the gearbox out of the lower receiver. This guide
is assuming you already know how to remove the retractable stock.
Step 1: Remove the lower half of the SIR. Refer to
this guide if you dont know how. 
Step 2: Cut the heat shrink tubing to free the quick disconnect
tabs.
Step 3: Using the quick take down feature break the gun open as
shown. Carefully slide the wires through the hole in the upper in
the direction of the blue arrow.
Step 4: Once the wires are out of the upper the two halves of the
body can be seperated by removing the front receiver pin.
Step 5: Remove the mag catch assembly by undoing the screw showing.
Step 6: Remove the feed tube and wire retainer.
Step 7: Remove the mechbox pin with a reamer or punch.
Step 8: Turn the gun over and undo the two screws on the motor base
plate. Dont touch the small set screw in the middle.
Step 9: Pull the base plate off making sure you dont lose the motor
shim and pull the motor out as well. Remove the two screws shown
inside the handgrip.
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Step 10: Once you pull the pistol grip off you should have something
like this.
CA gun shown.
Step 11: The gearbox is now free from the lower receiver set the
fire selector as shown and pull the gearbox out from the rear. You
may need to press the trigger to get it out.
