You only need an extended tube for the shotgun. Most 3-gunners are very generous and they lend you or help you with equipment at the match, especially juniors. What scope are you using on the AR? Vortex has a nice inexpensive 1-6x scope. I've seen a lot of juniors come out with their fathers AR's decked out w/ Eotech's or Aimpoint and can't hit 100 yard steel, thus getting frustrated. You want to keep the junior engaged otherwise, they won't last long.