Structaural said:A pit bull has a bite strength of 2000psi - I wouldn't put your arm anyway near it's mouth unless you're forcing your arm down its throat (another alternative 'get killer dog off you' technique).
I didn't measure the force of a New Foundlander's bite, but he is not exactly a little dog (weights about 65-70 kg). What I did worked to halt his attacks on the little one.
I'm not an expert on dog behaviour but I would think that a normal dog shall not switch to attacking a human when he is attacking an other dog. His mind - and rage - is fixed on the dog, reason why his victim should be removed from the scene immediately.
salaam.