Amazing, the blackberries on my property just started blooming this week. The flavor will change as the fructose ferments, but it's good both ways.
A pound per gallon is good for beer or cider. 3-5 lbs per for wine. I had so many blackberries last year, I made wine (20 lbs), cider (7 lbs) and froze another 15 lbs. Made a cobbler last week.