I have order a JP Enterprises, GEN2 AR-10 Silent Captured Spring Builder Kit w/ Alternative Spring Pack, Standard and I want to run a magpul prs gen 3 stock on the stag 10 I have coming. I have researched everything else to do with this rifle but I can't for the life of me figure out what buffer tube I need to run the Jp scs and a prs stock. Can some one please clarify what buffer tube I need. It's all I have left to order