No. It dosen't hurt anything (I've got one, they're cheap) but it dosen't help either. I like the idea of the nylon between metal bits so they don't slap one another, but the rifle was built to work that way. If you start shooting heavier stuff now and then, it might be a good idea. (IE, slip it in if your shooting heavy stuff for moose hunting)
As Hungry would say, they're a solution to a problem that dosen't exist.