I've had great success with snares made from synthetic rope or cord. I generally use just a fixed running noose with fixed open eye. I prefer not to use a locking knot or device. I have had very few animals escape from my snares. I don't use a lock because I want the snare to drop off the animal if it breaks the anchor cord and gets away.
But I do wonder how I would fare if I had to use natural cordage for my snares. Nylon is strong, has elasticity, and is generally smooth enough to run nicely through the eye knot. Natural cordage may be fairly weak and it is often quite rough... therefore the noose would tend to 'grab' in the eye as it was being pulled shut.
I would be interested to learn what others might know about making successful natural snares, particularly for bigger animals. I've seen examples of what are believed to be N. American deer snares made from natural fiber, so I'm fairly sure it can be done.
By having a flexible snare anchor, some of the shock load on the cord is reduced. Similarly, by having a spring-up snare the animal cant lunge about as much to put a shock loading on the cord. I have also believed that an animal caught by the leg might not be able to load the cord as much as an animal harnessed around the neck with a snare.... but I'm not so sure about that having had a strong cord snare broken by sheep that accidentally got its leg caught in a neck snare I had set for some small pigs. But certainly a spring-up leg snare seems like it could be effective with less-than-perfect cordage. However I've never managed to catch a large animal in a leg snare much as I'd like to.
The use of a smooth ferrule (like a hollow bone) for the snare eye might overcome the rough closing problem that a simple eye knot would create.
Another way to get around the cordage problems is to not use any cord for critical parts of a trap. A deadfall doesn't require any cord. I've caught a number of rodents in simple deadfalls, my best experience being the time when I used a figure four trigger under a wooden nail case to catch a mouse on a building site. I reckon that dead mouse could have dang near been posted into the slot on a dvd player.
So I'd love to read about what you have experienced or have heard about. Thanks in advance. Meanwhile here are some pics from my experience:
Note the notched bait stick on this figure four trigger. With the baid firmly jammed in the split, the critter will push hard to get the bait out. The tail you can see protruding from under the rock belongs to a big rat.
I've caught several hogs in snares. This snare must have been a bit big and possibly been set a bit too low because the hog was caught by just its back hoof.