Is there a specialization to carry more grenades for the M320?
The FRAG perk, achieved at rank 20, has this description:
Additional MOLLE grenade pouches allow the soldier to carry a larger amount of hand grenades and 40mm grenades.
When you equip the frag perk:
You get 1 more grenade, going from 1 to 2.
I believe you only get 1 more 40mm grenade, going from 4 total (1/3) to 5 total (1/4)