This is the recoil system that works.
https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories&Category=4eeff98b-d9a6-40fd-be6b-ab2e44ec1080
What is the size of the gas port in the barrel.
That looks like a low mass BCG.
Where does the gas tube end in the receiver?