I was under the impression that silencers don’t help at all with HV rounds, as there’s still the sonic boom when the bullet leaves the barrel (silencer). Is that the case, or is it only people downrange who hear the crack as the bullet goes past them?
There is still a sonic boom, but each listener hears it as the bullet passes. The boom is “continuous” along the path of the bullet as long as it remains supersonic. It is much harder for a listener to localize the shooter than with an unsuppressed weapon, though, as he hears the crack from the bullet not the report from the gun. The .[300 Whisper](http:// .300 Whisper - Wikipedia) is an example of a cartridge designed around use in suppressors. There are others. A subsonic projectile is not necessarily lacking in useful levels of energy. Many cartridges, like the very popular .45 acp are subsonic in their standard loadings in unsuppressed weapons.