Mine has washers now
I never did figure out a use for the tubing.
As Ed has posted below and with good caution, leave it alone or be prepared for the outcome.
I have been into my B40 so much that the screws jump out of the stock without even touching them. I think they are communicating, here we go again!
I think there are only two pieces and I am not even sure about that, that I haven't fingered. I really enjoy the B40 and it is so accurate and smooth.