He has the right to refuse service to anyone he wants.
You have the right to spend your money where you feel welcomed.

By your description, I would guess that he had you pegged as a "tire-kicking time-waister". Right or wrong, he made the decision to invest his time with another customer. Maybe he just didn't like your look.

If it's possible, and if you care, clean yourself up and see if he treats you the same.

Having a gun drop shipped to his store will not make him any friendlier to you