This Assault Rifle features:

-capability of launching rubber bands fully automatic
-capacity of ~20 rubber bands (depends on what type)
-removeable magazine prop with mag release

Check out the video above to see it in action and how to operate it

The model consists of 878 Parts (not included)
And would cost about 90€ on Bricklink.com + Shipping/Fees (It depends on your country)

Recommended rubber bands:

Shooting ones: ~Ø60mm https://www.amazon.com/Alliance-42199-Non-Latex-Antimicrobial-contains/dp/B0017TPZNU/ref=sr_1_13?dchild=1&keywords=size+19+rubber+bands&qid=1603714542&sr=8-13

Mechanism:
~Ø15mm (Hair rubber bands) no specific link. Search on amazon