Have you weighed your arrow? I think it is heavier than 385ish. I'm wondering if you just took the grains per inch (9.5) multiplied by 29.5 inch arrow. If so, you are forgetting all of your components which are quite heavy (fletchings, insert). If you have actually weighed the entire arrow, then disregard my post, otherwise see if you can find a grain scale and weigh the entire arrow.
Good point, I haven't actually weighed my arrow on a grains scale and I should definately do that.