How do motion constraints work?

[Gherkinman]

I'm having a problem getting some constraints to work properly. Basically, I made some pneumatic pistons and constrained the bore to the tube. They line up properly but the tube sticks out the same direction as the bore instead of towards it, so the bore isnt inside the tube like it should be. I cant just flip the tube around because the contraint "works" and the two parts move together.

I tried isolating and editing the whole assembly but when i edit it, it appears fine. Then I finish edit and it's backwards again.

I figure if I can somehow contrain the bore to move only within the tube caps it will both:a) Not look so bad by sticking out if its moved too far and, b) Actually get in the tube!

Can anybody provide some insight on this dellemma/ tell me how i can take a screenshot so i can explain it better? Thanks.