The legs for both BJG and Australorp should be black. The BJG should have yellow feet bottoms, while the Australorp has pink/flesh colored feet bottoms. A BJG has a flat back, an Australorp has more of a curved back.
we’ve had an Australorp male until he was 11 months old. We currently have two 4 month old and one 20 month old BJG males.
your male looks a lot like a BJG in body shape, and feathering, but legs aren’t that dark -should be darker. Per standard his tail would be wrong too, as it should be wide/spreading and at a 45 degree angle off the back. An Australorp tail is more classic upright, with the longer tail feathers typically associated with Roosters.
@EggWalrus mentioned Black Orpington, but I’m not familiar with that breed, so I can’t make a comparison.
still, a handsome cockerel!