years ago I read an extract out of a book written by a pointman in Nam, can't remember what unit or team he served with
He decided that when you make contact as a pointman in the bush it's important to saturated the target with a lot of bullets, as fast as possible
But also to raise the level of intimidation.
He said that when the enemy thinks he is being engaged with larger caliber weapons then he thinks he will be encountering in the "normal" type of jungle engagement, he might decide to bury his head a little bit deeper in the mud, and by doing so can't engage you, and you have an opportunity to break contact, or at least try
And stealing a flashhider from an ARVN's M3A1 was a good plan to raise the noise, on an already pretty load weapon
the pistol grip he attached just to keep it controllable, when going full auto. He said they kicked like crazy.
The "first contact mag" he used was also full tracer, to let the rest of the team know in what direction to shoot at.
I know there are pics of other types noise enhancers, flashhiders, some SOG's pointmen used them to and experimented with them