Monster hunter tri wii bowgun ammo?

ik how you can choose your own ammo and use it, but for example i hav recovery shots lvl 1 but i also hav lvl 2 but lvl 2 isnt an option wen scrolling thru my ammo. i do hav 22 slots in my item pouch full of ammunition but i tried emptying 3 slots of ammo that were available but still none of my newer ammo is available how do i get the ammo thats not showing up to be usable?