Does leveling up the Allie Tunisia smle mk III grenade launcher affect only shooting

Does leveling up the Allie Tunisia smle mk III grenade launcher affect only shooting with bullets or even the shooting with grenades? I mean is it worth it to level up the gun if I only use it as grenade launcher?

only to this

Sorry? Leveling up the gun only affects the normal bullets?

yes

Dang, good to know, thanks