What makes the noise when a rifle is fired?

Question

I'm sure its when the powder ignites. But I've heard its also from when the bullet breaks the sound barrier, ---if so, how much louder is this sound from the powder ignition? Where is the majority of the noise from.

The reason I'm asking is because I'm thinking about building an outdoor shooting range with a shooting shed to dampen or perhaps eliminate the noise so it doesn't bother the neighbors.

old fuzz, I'm not sure yet how far down range it should extend, thats what I'm trying to find out. I may use some material called Audioseal for soundproofing.

Doc, I'm curios about this muffler thing. But wont an extended shed with soundproofing work like a giant muffler if you build it long enough?

Answer 1

You can see the difference yourself. Go to youtube and look up some videos. There are some where people use a silencer but with supersonic ammunition. There are also videos of silenced weapons with subsonic ammo. With the subsonic loads you don't have the crack you would normally hear with supersonic loads.

Answer 2

Gun powder does not explode, it burns rapidly. In almost all rifles (.22 rifles with standard velocity ammo and a few others are the exception) the bullet leaves the barrel above the speed of sound. This does produce I higher pitched crack that usually cannot be heard over the sound of the gun being fired. You can here quite well if you are down range (ask anyone who has worked the target pits on a rifle range). The noise from the muzzle is the high pressure gasses being suddenly released when the bullet leaves the barrel. This is the same principle as the noise made when you pop a balloon.

Answer 3

The sound comes from three sources.

First, the primer, aka cap, explodes when struck by a firing pin.

Second, the powder charge quickly ignites, producing a huge quantity of gas in comparison of the quantity of powder burned. This expanding gas propells the bullet down the bore, and when it emerges from the bore, it releases the compressed gases, which produce blast. This is the loudest component of muzzle-blast.

Third, if the bullet is moving a supersonic speeds, the sound of the bullet breaking the speed of sound will add to the noise. At the muzzle, the blast of the powder gases generally drown out the sonic boom, but further downrange, a passing bullet can be heard distinctly breaking the sound barrier with a crack.

Forget about trying to dampen the sound of gun fire with an extended shooting shed, or soundproofing material on the shed's roof or sides. It won't work.

You need to build yourself a muffler.

You can do it two ways. You can build a framework, or you can build a berm to hold a framework. Use old truck tires stacked about six to fifteen feen long, you will have to experiment because it will vary depending on what you are shooting.

Shoot with the muzzle of your rifle or handgun within the bead of the end tire, and sight down the center of the stack of tires. The tires will act like the baffles in a sound suppressor and will muffle the sound of the gun's report.

On the down side, it will limit lateral use of your range, and is most useful for benchrest shooting rifles rather than IPSC type shooting with a handgun.

Doc

Answer 4

The rapid expansion of gases when the powder ignites is the cause of the loudest noise. The noise of the bullet breaking the sound barrier is inconsequential. Compare the sound of blanks to loaded rounds-virtually no difference.
The noise heard by the neighbors is dependant on the caliber of the gun you plan to shoot. You could conceiveably shoot a .17HMR or .22 with subsonic ammunition in your backyard without a shed. But if you plan on shooting larger centerfire rifle, you'll need some good sound suppression. Concrete walls are a consideration. Old mattresses do help-but not much. You could try thick panels of stryrofoam or similar items-but at the terminal end you'll probably want to opt for concrete.
Have you considered underground? Simply dig a trench from your cellar the appropriate length and box it in with concrete. The dimensions can be small-maybe 2 feet square. Then cut a hole in your cellar wall and rig up a pulley system.

BTW-silencers work by redirecting the expanding gases-not reducing them. Think of an exhaust baffle. There are the same amount of gases-but more ways for them to escape thereby reduciing pressures.

Answer 5

True, super-sonic calibers tend to be a tad more noisey due to the sound of the bullet breaking the sound barrier (and you can note the sonic "crack"). Most center-fire rifle rounds are indeed super sonic.

However, most of the noise comes from the expansion of the propellant beyond the barrel.

When firing a round, the noise isn't the "explosion" (ignition) per se, rather its the rapid expansion of the gasses.

You could ignite powder (black or smokeless) outside a firearm, outside a case, and it will just flame near-silently.

When the primer ignites the powder charge in a cartridge, the powder mostly if not entirely burns before it exits the barrel, but there are THOUSANDS of pounds of pressure behind it of the expanding gasses. As these rapidly expand and exit the barrel they create noise. This is similar to how thunder is created in the atmosphere during a storm.

A shed won't really keep the noise in - it will still go out in the direction you are shooting. And worse yet, the sound that is held in will bounce around the building and possibly damage your hearing if your protection isn't up to eliminating the decibles.

Answer 6

I am going to say that 75% of the noise in firing a firearm is from the rapidly expanding gas. The other 25% is from the bullet.

The bullet on all modern rifles are supersonic in the barrel they pass threw the sound barrier once exiting the barrel . The speed of sounds is 1037.2 fps. The 223 is moving at almost 3 times that at the end of the barrel. Just like when airplanes break the sounds barrier they cause a sonic boom. Bullets do the same thing it is not as loud as an air plane because the bullets are much smaller in size and weight.

I seen a set up once where the guy had 4 55gal plastic drums set end to end and lined with egg crate foam to dappen the noise form shooting.

My dad tried to used ten feet of tires full of egg crate foam but it did not work the well because of the bullet being supersonic.

Answer 7

Just to cement this in: The bang is from the rapid expansion of gases from the barrel, period. The round breaking the sound barrier will make a snap noise down range but is minor and often isn't heard at all unless you are rather close to the round going by!!

As I answered in your other question, don't bother trying to soundproof an outdoor range for large caliber rifles, it is damn near impossible and would be extremely expensive. Go the underground route.

Answer 8

A 22lr is fairly quiet out of a rifle, fairly loud out of a pistol. Barrel length and powder charge are the biggest contributors. Powder charge will be the same in the same round, but barrel length changed.

Answer 9

Think of it this way.* If you fill a paper bag or balloon with air and then crush it or smack it together with your two hands, you will understand that it is the force of the air suddenly released that creates the noise, and the same thing happens when the gases behind the bullet suddenly exit the end of the barrel or muzzle of the gun.*

Answer 10

You are basically correct, except the noise is from the expansion pressure of the powder after it has burned. The bang is the 50,000 lbs/psi average rifle pressure exiting the front of the barrel. Combined with the bullet breaking the sound barrier makes the noise you hear.