Big bang
And for $85 you can have one too!
https://stsfirearms.com/product/loudener/
Is this like the coal rolling thing, where "triggering the libs" by being obnoxious, harmful and irresponsible is the only point?
It's a joke because it largely wouldn't do anything but possibly make the gun a very little bit quieter for those around it while also making you completely unable to aim the thing because it obstructs the sights.
https://www.youtube.com/watch?v=-WKM9GDuX0Y