Nvacca88

So i was planning on picking up a Saiga 7.62x39 and when i called the gun shop they mentioned i had to be 21, im 20 right now but as far as i knew you only have to be 18 in florida to purchase a rifle(considering i already have a Ruger mini 14 and a Rem 870 both purchased by me) Is there something ddifferent with this classification of rifle that i am not seeing here? Why would i have to be 21 if the State law clearly syays 18 for rifles. Thanks for the help