The main issue with the M320 is that it requires loading every time you equip it and unloading it when you unequip, unlike nearly every other grenade launcher in the game. Even with the Turkish/WPMC MGL you can just pull it out, flip off the safety and then you can fire all 6 rounds.
With most grenade launchers in the game, a load animation only occurs when you're switching to smoke rounds or transitioning from smoke to HE. When you switch from rifle to grenade launcher (HE Rounds), the animation typically just involves flipping up the sight and taking off the safety.
So I am suggesting that the M320 have the same animation sequence as every other GL in-game.