You might look at the following portable buck saw:

http://www.leevalley.com/garden/page.aspx?c=2&p=44171&cat=2,42706,40721

I have had both sizes for many years. The smaller one is in my bug out bag and the larger one is in my truck. There is no springs to loose. You can also get a bone saw blade for butching. With a little finesse, you can store two blades inside when collasped. You can cut much larger diameter logs than a sven saw. Search the web for other venders for the bone blade.

My wife thinks I have every saw know to man. I do have my own wood lot, have my own band saw mill, many chain saws, inaddition to many old logging hand saws. They are all very usefull. However, I don't want to carry anyone of them, their fuel, or their maintenance supplies.