Way back then accuracy stat was relevant for projectile weapons, because if a xeno was moving and your shot would connect, it would still fly past the xeno and give you the message “the rifle bullet narrowly misses Lurker(XX-121).”
So in short accuracy is a probability variable of whether your shot is going to actually land on the target it was aimed at. This is relevant for projectile weapons mostly.
As the GL does not work with a projectile, but rather “throws” a grenade, this is not going to affect the weapon I believe. Additionally accuracy of zero, means it will stay zero whenever multiplied.
Spread however, is the one that deviates shots from where you are aiming at, by changing the path of the projectile. GL has no spread either.
That is the difference between the two.
So go ahead, put the Magharness on it like you’re supposed to.