dog breed?

[Miakoda]

They do, maybe not that big, but I'm also guessing that since he was a shelter dog, he doesn't have the best breeding behind him. Mastiffs seem to develop underbites pretty quickly anyway, even in good lines. And if he does have some boxer in him, they all have underbites, so that would make sense.

I agree. Backyard breeders put out a wide variety of dogs and they don't always showcase the standard traits.

IMO this is a bullmastiff mix at least and very possibly a Bullmastiff/Boxer mix.

The body of that dog is waaaaay to big to be a "pit bull's" body.

 

[Squishy22]

My guess is bull mastiff/boxer.

 

[robstaine]

Miakoda. see in that picture you have by every comment you make.. what breed is that? he looks like yours body wise by bigger, it is possible that he may have pit in him... he could be bullmastiff cross pit now adays there are a lot of different sized pits, they may not be full ones but it still has pit in them.