Seriously , I have a big clunky table saw in my basement. I can take one big split log and make it into a whole bag of chunks like you get at HD (for about 9 bucks). This way costs me zip.
Just start it so the saw blade doesn't hit an edge first and you should be fine. Wear a glove on the hand holding the wood, I lost a large chunk of skin and quite a bit of blood when the split spun on me once when the blade grabbed.
I use a sawzall with a pruning blade, or my handheld bow saw.
Using a miter box to cut an irregular shape not held against the fence or table squarely is an accident waiting to happen.
Easier said than done with an irregular shape like a limb. A miter box forces (with the downward motion and blade rotation) the waste piece towards the table (bottom) and the fence (back).
If you have a slight crown up or towards you,than you stand a good chance of getting a kick-back. Not a big deal if you don't mind ruining a perfectly good tool not designed for using it for that purpose.
You can take one to the face or body, your call, but I personally wouldn't recommend using one for that purpose to anybody.
I'm a Carpenter and run a miter box all day, and have three personal ones in my garage, and I would never, ever use one for cutting limbs.
I also use a chop saw to cut pieces into rounds that are about 2 inches thick. I then but the pieces on a concrete floor (my garage), place a hatchet on the blocks and split the blovks by hitting the hatchet with a rubber mallet. This lets me control the size of the chunks.
Ray
Nothing should go on a chop saw that isn't already machined (straight) on at least 2 sides...the one down on the table and the one back against the fence.
I use a band saw for cutting splits into chunks. Even that is not ideal. Irregular surfaces and powerful stationary machinery don't mix well. The reciprocating saw (Sawzall) is a safe method, but time consuming.
Having used a lot of cordless tools, I have to wonder what the battery life of that would be, but...if they have a good battery design, it looks like a very safe option for those who aren't experienced with chainsaws.