I tried using the 5/16" but I rarely found dowels that were spined heavy enough. I use the 3/8" dowels. First I check all shafts for grain run off. Pick only shafts that run true. You might have to stand at the dowel bin for sometime and endure looks from other customers. Also look for shafts that are straighter with only slight, or sweeping bends. The ones with radical bends have never worked out for me. Then I straighten them with heat and a hook.

I sand them down, with a drill, until they spine correctly. That usually leaves them about 11/32's. After they are spined I fire harden the first 6 or 7 inches, and them seal them.

The finished arrows look good and stay straight. Most of the time I finish them off with a Massey finish. Hard arrows and a hard finish.