I know this is an old thread, but it seems to be what we are experiencing…so rather than start a new one, I thought building on an old one would be best.
We adopted a brother/sister pair of 5 month old Bs. They do well with other dogs, rarely nip at other dogs (unless they are overly excited and the other dog is a little too friendly - nothing serious so far), but my goodness do they roughhouse with each other.
They will start the B-500 while taking them for a walk, and wrestle and tackle, nibble, grab each other by the throat, ear, leg, etc. Sometimes there's noise, sometimes not, lots of legs flying everywhere as they wrestle each other to the ground. By what I've read so far using the search feature, this seems pretty normal B behavior. But occasionally we fear someone's going to call the police and tell them we have a dog fighting ring going! Luckily for us it's only with each other that they wrestle. Other dogs don't interest them except to prove they can run faster.
So the $64,000 question is...should we try to train this out of them, or do we just need to learn to live with it - as long as they keep it to themselves and don't involve other dogs.