We highly recommend you do not wait to purchase ammunition the day of the class. Ammo availability is scarce and intermittent sometimes. If you are bringing your own gun, the best policy is to check with the range hosting the class to be certain they have ammo available. If you are renting a firearm, then it is most often the policy of the range that you must use ammo they sell you to shoot their guns. Either way, plan ahead and make sure you have what you need before the day of the class.