5 Surprising Facts About Gun Silencers

Gunshots are loud because superheated gases expand rapidly and produce shockwaves as they escape the gun's chamber. Silencers contain a series of expansion chambers that cool and dissipate the gases before they leave the barrel.

A silencer is a lot like the muffler on your car (in fact, both were invented by the same guy). Screwing a silencer onto the barrel of a gun doesn't "silence" the explosive bang, it just muffles the noise. That's why folks in the gun industry call them suppressors instead of silencers.

The decibel level of an un-suppressed 12-gauge shotgun is 160 decibels, louder than standing on the runway when a jet is taking off (150 decibels). The Occupational Safety and Health Administration (OSHA) sets 140 decibels as the threshold of pain, although it takes far less than 140 decibels to inflict long-term hearing damage with repeated exposure.

According to a fact sheet from SilencerCo, a Utah-based silencer manufacturer, a 12-gauge shotgun equipped with a silencer registers 137 decibels and a silenced .22 rifle is muffled to 116 decibels, slightly louder than an ambulance siren. Still loud, just not eardrum-busting loud. 

That may explain why, contrary to popular belief, silencers are seldom used in criminal acts. One study looked at federal court cases involving silencers reported in the Lexis/Westlaw database between 1995 and 2005. Of the 153 cases reported, just two cases involved a silencer being used in a murder case, and overall, only 12 involved the use of a silencer in the commission of a crime. Gun control advocates, however, point out that silencers have been used in some high-profile crimes.

There are currently 42 states in the U.S. where it's legal to own a silencer, and 40 of these states have legalized silencers for hunting. The main states where silencers are illegal to own or use for any purpose are California, New York, Illinois, New Jersey and Massachusetts.

Silencers are regulated under a 1934 law called the National Firearms Act (NFA). Although many people think that silencers were banned in the 1930s to fight a rash of Mafia-style killings, The Washington Post reports that authorities were more afraid that poachers would use silencers during Depression-era food shortages to hunt out of season.

In fact, the NFA never made silencers illegal. It simply included them among other exotic firearms and accessories — machine guns, most notably — that require a special tax to purchase. If you want to buy a silencer in any of those 42 states today, you have to pay a $200 tax to the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).

Even though silencers are legal in dozens of states, that doesn't mean they're easy to buy. There are thousands of gun shops nationwide selling popular brands like SilencerCo and Liberty Suppressors, but the only way you're going to walk out of the store with a new silencer is if you pass the ATF background check. And that can take up to nine months.

Here's a simplified view of how the process works: You purchase the silencer at the gun dealer and get a serial number for it. You'll need that number when you fill out ATF Form 4, "Application for Tax Paid Transfer and Registration of Firearm." You'll pay the $200 tax required by the National Firearms Act, and also attach a passport photo, fingerprint cards and answer a bunch of background questions — are you a fugitive of justice? are you addicted to marijuana or other controlled substance? — that could disqualify you from purchasing a silencer. After the ATF approves your application, you can collect your silencer. If you do buy online, the silencer is shipped to a dealer after you're approved. You can read more about the whole process here.

The American Suppressor Association, a silencer industry advocacy group, estimates that an ATF background check typically takes between four and nine months. This is the main obstacle to legal ownership that the silencer industry wants to see abolished.

The gun industry is positioning silencers as a health issue. In fact, the bill that would eliminate the $200 tax and ATF background check for buying a silencer is called the Hearing Protection Act. There's no doubt that repeated short-range exposure to gun blasts will inflict lasting hearing damage. But why can't hunters and other sportsman simply wear ear plugs?

The American Suppressor Association argues that many hunters don't wear ear protection because they want to be aware of their surroundings. It's hard to hear the call of a migrating duck or the sound of a buck moving stealthily through the underbrush if you're wearing earplugs or noise-reducing earmuffs. With silencers, gun advocates argue, hunters don't have to sacrifice awareness for safety.

Another safety benefit touted by the silencer industry is accuracy. The anticipation of a loud blast causes some shooters to flinch as they pull the trigger. This may lead to inaccurate shots, which could endanger other hunters or result in an injury to the animal.

A shotgun silencer from SilencerCo retails for $1,440 and even its smallest products, like the 6.5-ounce Rimfire, sell for more than $500. For that price, you can see why some gun enthusiasts prefer to make their own silencers out of common household objects like oil filters and flashlights.

First, it should be said that the only way to legally make and use your own silencer is to fill out ATF Form 1, "Application to Make and Register a Firearm." Again, that comes with a $200 tax and a months-long waiting period.

The Maglite suppressor, made from the industrial-strength flashlight, is one of the most popular DIY silencers on the internet. The key to all DIY silencers is getting an adapter with the right threading to attach to the barrel and whatever you are using as a makeshift suppressor.

Another popular option is to use an oil filter or a fuel filter for a car, otherwise known as a "Tennessee silencer." You can find any number of detailed video tutorials online for assembling a filter-based silencer that won't cost you more than $20 in parts, plus that $200 tax, of course.

One word of warning: If you're determined to make a silencer a DIY project, be sure to stay on the right side of the law and be careful not to physically endanger yourself in the process.