Depends on the state you are in. Some states tell you which sizes are legal.
Edit to add: Looking at the 'Bama regs., I would venture to guess that as long as you stay with #4 - 000 buck you'll be fine. T and F are offered in Steel so they would likely be considered to be waterfowl shot. The officer's interpretation will win in the field and I would hate for you to have to get a decision in court.
Last edited by SHR970; November 20, 2012 at 08:28 PM.