After playing around with the latest dev branch of Arma 3 (version 1.55.133167),
I experienced, that the reload sound of the 3GL (MX 3GL) doesn't match the reload animation.
We have two different types of underslung grenade launchers:
The EGLM and the 3GL
Both grenade launchers have their own nice reload animation (at least in the dev branch) but the same reload sound.
It would be nice, if you tweak the reload animation of the 3GL (or create a new one).
For now, the sound doesn't fit the animation. The animation is much faster than the reload sound effect.