LG: Yes, the purpose of the compression spring is to keep a constant tension on the animal and make the snare more lethal. A lock equipped with a spring like this is not
a relaxing lock. This set up would be illegal to use in Ohio and a number of other states.
Red: After than long discussion on BADs, I did find documentation for this test. It was done by Phillips, Blom, and Johnson at the Denver Wildlife Research Center. From a report titled "Evaluation of Breakaway Snares for Use in Coyote Control" published in 1990 (Univ. CA Davis) I quote: "To our knowledge there have been no established techniques for testing the physical strength characteristics of snares…"
"Samples of each type of snare (n=12) were connected to a Southwark-Emery universal testing machine… to determine the tension required to break the locks or release mechanisms. Each snare was attached… by placing the snare loop around a 3-in diameter steel rod… As the machine slowly tightened the snare loop… maximum tension was recorded when the snare lock or release mechanism separated from the snare."
"This testing procedure was not intended to simulate the forces an animal applies when captured by a snare. However, it did allow us to develop a standardized comparison for snare locks when they are subjected to a slow and steady pull…"
This is the documentation I had been looking for all along. Since this is the only scientific documentation I can find, I assume there are no other sanctioned competing tests, and the test as described forms a bench mark for comparison of the sundry devices out there. (I'm still exceedingly curious at to what value a 90 lb BAD would be.)