There still seems to be some confusion so I'll take a stab. :)
First off a definition: "Torklift mount" the part that attaches to the frame including the removable insert.
The Fastguns come in two lengths and connect between the "Torklift mount" and the tie down points on the camper. The short Fastgun most likely will require a short chain or similar connection unless connecting to the front Happijac mount.
I have four of the long (and adjustable) Fastguns. All have built in spring tensioners as do all Fastguns per Torklifts web site.
OP are you sure you have two Fastguns without spring tensioners or something similar that look like Fastguns? I suppose its possible the spring mechanism has failed in those two.