I have refurbished several AR units over the years and think that while there should be some, the amount of play between the inner and outer should not be excessive. The centre will be held on the mag spindle and too much play will allow the fiber pinion to move around relative to the camshaft pinion which drives it and destroy the fiber gear. I would say upto about 25 - 30 thou play on the outer edge of the fiber wheel would be ok. [in my opinion]
You need to take it apart and clean any gunge out of it before you can assess how much play you have. Sometimes they can be stuck together with crud which hides any wear. If it's in good nick, its a fairly easy job to fit a new fiber and springs.
If you want, post it to me and I will take a look at for you, [FOC], if its ok I could give it a bit of an overhaul and fit you a new fiber pinion. PM me if you like.