"strikefast"Sprocket, The saw blades are fine. They will take the impact and the pellets should only flatten. Keep in mind I would reconsider if you are shooting a .30 cal or larger and over 50 FPE.
If you put the saw blade behind a piece of plywood with a large enough hole to your liking, or several, it will be safer as the pellets would just bounce off the blade and then the wood. Here is a picture of what you can do in wood. Just need the blade, 2 nuts and a bolt.
I make targets, and this is one I made for me, to tell how far the wind pushes my 12 FPE Styer I use for WFTF practice. I also included a link to a film on how it works and sounds. I used a thick aluminum disk for mine. Have fun building and shooting your saw blade!