What is the legal purchase age for an AR? I know pistols are 21 and shotguns/rifles are 18....in FL atleast. If it makes a difference im 19 years old and an active duty Marine... Another question, what do yall recommend for my first AR15 build, start from scratch with a empty lower and build up? Or take the easier way out and pick up a Stag, Bushmaster, RRA, etc. and build it into the weapon I want it to be?