Preheat oven to 375°F with rack in middle. Butter muffin pan.
Whisk together flour, oat bran, sugar, baking powder, baking soda, salt, and cinnamon in a large bowl.
In a separate bowl, whisk together buttermilk, honey, butter, and eggs. Add to dry ingredients along with raisins and stir until just combined.
Divide batter among muffin cups. Bake until a wooden pick inserted into center of a muffin comes out clean, about 20 minutes. Turn out onto a rack to cool.