How can I hang a wall bracket for a punchbag in the inside of my home?

Hi everyone, I have a problem. I have a spare room in the upstairs of the house where I wanted to hang a wall bracket for my punchbag. The instructions say that I need a 14.5mm(masonry drill bit) a hammer drill, and some 55mm plugs. The idea was to drill the holes in the gable end wall on the inside of the house, but the problem is that there's a thick layer of plaster coating the wall, which crumbles when I drill into it, before you reach the brickwork. Can anyone suggest a way that I can hang the bracket from the wall on the inside of my house? I am stuck, thanks.