Hi Billy,
Josh is correct about the line lengths. In a normal situation the "stretch" Josh refers to is being absorbed over a long distance ( hopefully with a
on the other end). That distance is key as pressure is distributed over the length of the line. In your experiment the pressure has only a few feet to travel across, which I think could be part of your "test" problem.
The other aspect you might want to consider is doing a blind test. Testing each line independently to see if you achieve a break point similar to the manufacturers to rule out bad batch.
Here are a couple of good links that you might find helpful.
http://www.stripersonline.com/surfta...d.php?t=497830
http://www.sportfishingmag.com/article.jsp?ID=43557
best,
Josh