How a gun silencer work?
In: Physics
Silencers/suppressors/mufflers/cans slow down the expansion of the gases ejected at the muzzle when a bullet exits the barrel. These gases are what was projecting the bullet.
When they suddenly are allowed to exit in nearly all directions, as well as meet fresh oxygen and relatively cold air, you hear a boom and see a fireball. When the bullet breaks the sound barrier (1060 to 1200 fps depending on the environment), there is also a crack sound.
The silencer constricts these gases into a device that is specifically made to slow them down, usually by having them run into a series of walls (baffles). The spacing and amount of these walls have different effects on the silencer’s performance. Many companies have many different takes on what works best in terms of actual decibel reduction for a specific use-case.
Because these gases are cooling down more slowly and slowing down more quickly (a few milliseconds) the sound of the gases exiting the “muzzle” of the suppressor is lower.
No silencer alone can eliminate the cracking sound of a supersonic bullet. This is why lots of silencer enthusiasts tell beginners that chasing raw decibel reduction for a caliber like the AR-15’s standard 5.56×45 is mostly futile.
Subsonic rounds do exist for traditionally supersonic calibers, which do not produce a cracking sound when breaking the sound barrier. However, if the round was not already on the border of breaking or not breaking the sound barrier, then they tend not to work well.
Thats why the Soviets never went through with making an integrally suppressed AK-74; the difference in lethality between subsonic and supersonic rounds was huge for that caliber. Which is where the 9×39 caliber was conceptualized.
There are some variants of guns which can take a supersonic round, and bleed off gasses into an integral suppressor early on, making the round subsonic upon exit.
The most famous of which is the MP5SD. But without a ported barrel, the rounds would still be supersonic; the can doesn’t change that, it just catches those gases so that there’s no explosive noise at the barrel port. Bullets fired from traditional suppressors are often marginally faster than their unsuppressed counterparts (take that, video games).
Not to mention, if F=m*a, and the mass remains constant, the slowing down of the bullet will in fact have a negative impact on the bullet’s performance, which is why lots of special secret squirrel units/agencies are ditching the MP5SD.
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