In Only War, do grenade launchers use the same grenades as the ones you can use as hand grenades? What about the auxiliary grenade launcher / underslung GL?
In the core Only War rule book there is the following sentence prefacing the table of explosives:
The explosives listed here can either be thrown by hand or loaded in a grenade launcher as grenades, used in missile launchers as missiles, or fired from mortars as rounds.
Additionally, the grenade launcher has the following bit of description:
The standard grenade launcher uses compressed gas charges to launch a variety of grenade types at the enemy.
Together, these lead me to believe that hand grenades and grenade launcher ammunition are in fact the same.