Well looking a little closer on wgc shop it looks like I can answer my own question. All the buffer tubes look to be attached the same way. Even the STAR brand ones. And considering I'm trying to put a trigger master in there too, I'm pretty much ruling out the buffer tube idea. I think I'm just going to use this with a trigger master and the batteries I have now:
http://www.wgcshop.com/pcart/shopper...16B_cat_Stocks
Anyways, thanks for the reply guys. (At least I know it's called a Castle Nut now. You learn something new everyday.)