I've had Troy for only 4 days and yesterday he did the same exact thing. 2 friends came to play with him (they love him already) last night and he snapped (he was tired). He began growling and even slight barking and began to bite really hard and tugging at what he was bitting (hands and fingers)
I understand when Troy is 'play-bitting' there is no real force exerted into it and i have no problem with it. But i got very disappointed last night, thinking something was troubling him. Now I believe he was just tired (he went to sleep minutes after the people left). Today I spoke to the vet about his episode and the vet told me that clapping my hands in front of him when he's bitting hard is the best approach. Low and behold i did it today and it worked like a charm.
I am not a fan of hitting, but can live with a slight tap on the butt (and when i say slight I mean just something to get his attention not to cause him pain) but when doing so I would suggest for anyone that it should NOT be done with the HAND. Remember the HAND pets and rubs the dog and it also feeds him/her it would be confusing for the dog if he/she also got hit with it. This is why you see many dogs pull back when an owner extends his/her hand at them.