Thanks for the info guys.
POF tells me they are not making that tube now because they do not make a rifle that takes it.
The tube is 7 9/16 inside, and has the anti-rotational lip at the buffer detent, that is why I like it.
As far as the spring, my bad choice of words, they say a factory DPMS rifle length 308 spring is the one to use. And a AR 5.56 buffer of your weight choice for your needs.
I was just wondering if anyone has used that set up to relay outcome. I would rather do this once, than have several tubes and buffers extra.