Place cornmeal in shallow dish. Dredge pickle spears in cornmeal & transfer to plate. Combine flour, cornstarch, baking powder, salt & cayenne in a large bowl. Slowly whisk in beer until smooth.
Heat oil in large dutch oven over medium high heat until 350 degrees F (or use deep fryer). Rewhisk batter. Transfer 1/2 of pickles to batter. One at a time, remove pickles from batter (allowing excess to drip back into bowl) & fry in hot oil until golden brown, 2 - 3 minutes. Drain pickles on wire rack set in rimmed baking sheet. Repeat with remaining pickles.