WARNING – Always wear safety glasses when assembling your firearm to protect your eyes from components that are under pressure which may be projected towards you.  


Refer to the Mongoose parts terminology as needed.



1. Fit the upper and lower receiver together. 


2. Insert the takedown pins.


3. Assemble the firing pin w/ spring back into the bolt (if removed for cleaning)


NOTE – Ensure the spring is still present on the firing pin before reassembling.


4. Assemble the barrel back into the bolt.

5. Make sure the takedown lever pin is pulled out to it’s fully extended position.

6. Slide the bolt assembly (spring first) into the upper receiver ensuring it’s lined up as shown in the photo.

7. Drop in the charging handle carrier.

8. Push the charging handle assembly back in to your preferred side.

9. Lock the bolt to the rear.

10. Push the charging handle to the forward position.

11. Push the takedown lever back in and rotate counterclockwise to lock.

12. Depress the arms of the front compensator cap as you push it back into place.

13. Check that the bolt operates correctly by releasing the bolt forward with the bolt release lever.  pulling it back to a locked position and release it with bolt release lever.

14. Leave the chamber clear with bolt locked open and leave the magazine outside of the firearm until you are ready to shoot.