Lower Receivers & Parts. Showing all 8. AR-10® pivot pin. $6.00. AR-10® take down pin – Oversized. $10.00. AR-10® B-Series Stripped Lower Receiver.Lower Receiver Parts. Showing. AR-10® A-series bolt stop replacement kit. $ 18.50. AR-10® spring replacement kit (to be used with 2-stage trigger). $16.00.Also, you're building a AR 308 not a AR10; two different systems with compatibility issues.. .. Matrix Aerospace Armalite pattern matched upper and lower receiver set (forg. Items 1 - 9 of 18 . Browse, compare and shop for your AR-10 Upper and Lower Combo Set.. Low- Pro · LUTH-AR · LWRC International · Manticore Arms ·. As we move forward into a new millennium, Matrix Aerospace continues to partner with aerospace, military, firearms and are Lockheed Martin, Raytheon, BAE Systems, Barnes Aero. I really like the maten I just built.. I am assuming the threads etc on AR10 and AR308/DPMS/SR25 ( sigh.. A company called Matrix Aerospace makes the receiver sets Ruger.. .