Can I buy a pistol in AZ at age 20?

I am 20 years old In Flagstaff, AZ and I want to buy a sidearm for everyday carry. Exhaustive google searching and a trip to my local PD told me that I can buy, own, and open carry a handgun. However, all of the FFL dealers I have been to say that I have to be 21. Can I only buy in a private sale? Is it the same with ammunition? What about classes in tactical handgun use? I would prefer answers from folks with experience in this area. Links to the specific, relevant laws would also be appreciated. Simply telling me to wait until I am 21 is not an acceptable answer. Thanks.