what' s this book called?

[black bunny]

This is really driving me nuts trying to remember this book. I read it in paperback early 70s when I was in my early teens, I think it was published round about then. The story went something like this...
Man's girlfriend or wife is murdered by or dies at the hands of Hells Angels.Man is hearbroken but vows to avenge her death, and becomes an undercover Hells Angel. He has to do all the usual rituals to prove he's serious about being a H.A. At the end of the story he's got his revenge and killed the culprit, and he dies too, in some violent way.
I'm really hoping someone, perhaps about my age, has read and recognises this story. Please put me out my misery and tell me the title and author! I'm counting on you all!