What have you tried to stop him doing it?

You shouldnt muzzle a baby, You didnt muzzle you child when they were putting everything in thier mouth did you? its the same he hasnt got hands to play with things he only has his mouth yes he might be going hard but that where he need guidence to show/tell him hes gone to far and that it hurts

Zeb was a nipper he would nip hard aswell if one of the kids ran he ran with them and would nip them, A quick OUCH in a very high pitch would stop him and then we would say "no bite" and turn away from him, It didnt take long before he realise we wouldnt play with him if he was biting hard

__________________
Owner to-
lots of rodents
2 monster dogs
1 slinky cat