Seems like certain powders sound different than others. This was true of H870 in the 7RM especially at a distance. If there is a difference what are the quieter powders? Is it the burn rate and amount of powder or other factors?

Difference might be due to "exit pressure" at the muzzle ? Interesting question.

Exit pressure relates to gas jet velocity.

Like H335 in a 556 rifle,at night.

It's louder than some other powders and it can cook your lunch.

Craigster has it right. The amount of sound is determined by the pressure of the gas when the bullet exits the muzzle.

Shorter barrel = more pressure.

Longer barrel = less pressure.

Larger charge of longer burning powder = more pressure at bullet exit.

All that said, you're not likely to take much notice of 3dB differences (-50%, +100%).

That gas jet is what generates felt recoil too. When the bullet clears the barrel that gas hits the amosphere and pushes the rifle back into your shoulder.

I shot Hi-Power rifle silhouette with a Canadian shooter who used a 308 Win, using Scot powder - it was easy to tell when he was shooting, the noise from his rifle sounded more like a black-powder load than a smokeless load. I have no idea of what velocities he was getting but his load knocked the animals over as well as anyone elses.

So yes I am convinced that different powders can create different sound effects - I just don't know the science behind it. I shot a max + load out of my 22" barrel 243 and it was noisy enough that no one wanted to shoot next to me, so out of consideration I would step as far forward of the other shooters as possible so they did not catch the full muzzle blast effect.

drover

H110 is one of those powders that everyone at the range knows you're shooting. The first time I took a starter load out to the range to try it in my Super Blackhawk, the range saftey officer came running over; he thought I'd blown up the gun.

Now that I am firing 44 Mag out of a semi-auto rifle, I don't notice it nearly as much.beginning

Shooting max loads of Viht N560 and RL26 in a 243 Featherweight, the RL26 seemed considerably quieter with less recoil to me. Completely different manners in the rifle.

This all sounds logical. But I would propose there is at least one additional variable: perhaps direction of exiting gasses?

Witness the "loudness" of a rifle with a muzzle brake versus a similar rifle without a brake.

Blue Dot in a revolver has gigantic flash and is very loud.The plus is it is very accurate,

The gas "hitting the atmosphere" is not what does it.

It does when I fart.Loud and heavy recoil.

If you look at Speer #11 for 357 magnum they list the max pressure as 46000 cup. With a 125 grain bullet the max load of Blue Dot is 16.3 grains.

Speer #12 has 35000 psi and 13 grains.

In the 90's a buddy bought a 4" barreled GP100, a stout 357 for sure. He asked me to put together a few rounds for him so I did, to the older spec of course. When he fired the metal roof over the firing line sang for a bit. To this day that load is known as The Roof Ringer.

Loud needs the atmosphere, recoil doesn't.

HUH? WHAT did you SAY?

Yep😁 good way to put it.

Umm, no. It is not the "gas jet hitting the atmosphere". The recoil is a simple conservation of momentum.

(Mass of bullet x its velocity) + (mass of propellant x its velocity) = (mass of rifle x its velocity)

The rifle starts to move as the bullet starts to move. It is actually starting to recoil before the bullet leaves the muzzle. However the propellant exiting the muzzle, and due to overpressure doing so at a greater velocity than the bullet, certainly plays a significant part, simply by reason of the momentum it contributes to the system. It is nothing to do with "hitting the atmosphere and pushing" though, and would contribute to the recoil in vacuum in the same way.

The mass of propellant is often overlooked in thinking about recoil, and it is possible to have two loads with the same bullet at the same velocity, but significantly different recoil, if you change from a slow powder (and hence greater mass of powder) to a faster one (and hence less mass).

Of course the gas Mxv is vectorial too, and so you can also reduce recoil by redirecting it, such as into a gas piston, or via a brake or can.

Dan,

Exactly.

The only time something different occurs when the bullet leaves the muzzle is a bigger flash, due to the hot gas reigniting when "enriched" with oxygen. But that has nothing to do with recoil.

Many shooters think the big flash is due to powder that's still burning. But all the powder that was going to burn, did so long before the bullet exits.

When I took Acoustics in electrical engineering, the professor was Rubens Sigelman, ultrasound pioneer. The book was Kinsler
https://www.amazon.com/Fundamentals-Acoustics-Lawrence-Kinsler/dp/0471029335

I should have been able to figure this out:
Why does a 22 with 22" barrel sound like a loud gun, but a 22 with 24" barrel shooting rem CB longs sound like a BB gun? What is going on with 2 more inches of barrel?

I could not figure it out.

I asked proffesors. I asked everyone.
The late experimenter and gunsmith Randy Ketchum, said, "That is the threshold of supersonic gas escapement."
I knew he was right.
The gas ball at the muzzle would be noiseless until it slowed down to the speed of sound and then propagate a wave with harmonics rolling off at wavelengths below the gas ball size.. That is why cannons have a deep boom, like woofer speaker. 1000 Hz is a wavelength of 2.5 feet. A gas ball 2.5 feet wide would be attenuated at sounds lower than 1kHz, but still audible as low frequency carries further and around corners.

The next question I sought help on was "What is that threshold pressure?
The answer was from a guy whose on line image was a biker in CA with tattoos, strippers, and was a recording engineer. He calculated one atmosphere above ambient.
I knew that would be a natural threshold as a peak wave of 2A would have a trough of a 0A, which is the threshold of cavitation. Sound will not go lower than that.
So I knew he was right.

I started seeing the muzzle pressure in Quickload as being as high as 10 kpsi.
The problem with that is the chamber plus barrel volume will also affect the size of gas ball.

I began experimenting with what would kill big game, sound like a BB gun, and not have a suppressor.


This is several old 12 ga shotgun barrels with remchoke male threads on the breech and remchoke female threads on the muzzle.
The correct answer was not this. That is quiet, but awkward.


The correct answer was a 50 caliber rifle wildcat made from 56-50 brass with an extremely high expansion ratio.

You could take someone's eye out swinging that thing around

Hey filaman,

It might have an effect on "felt" recoil but it hasn't got much to do with mechanical recoil. By felt recoil, I mean you might "feel" or believe (big flash, maybe) it's affecting you more when in reality, it's not doing anymore than any other load of the same recoil energy level.
Mechanically, that jet doesn't rely on the atmosphere. If that were the case, spacecraft wouldn't function very well in space since their exhaust wouldn't have anything to push against. Instead, it's all about Newton's Third Law. Others above have already alluded to it so there's no need to rehash it here.
I also agree, exit pressure at the muzzle, the direction of that exit pressure (specific brake), the nature of the expansion wave play (what kind of "flashhider/thing on the end") or even the sheer volume of the pressure wave (artillery/tank) will play the biggest role in how loud something is or perceived.
Additionally, whether the shooter has good hearing or is partially deaf plays an important role. 😁

I’ve had several guys in our club tell me that my 35 Whelen has a distinctive sound.

As do AK 47s. Ask me how I know.

Semper Fi

Same deal with my wife when I was using a .338 Winchester Magnum with a 22-inch barrel to slay whitetails along a certain Montana creekbottom 30+ years ago. She would be sitting a few hundred yards away, and sometimes not only heard the bigger boom, but the thump of the bullet hitting the deer.

Dunno what all this means. Have killed a lot of big game, quite suddenly, with cartridges that made a lot less and (sometimes) more noise than that .338.

My 23 inch barreled 6.5x55 has, to me, a very distinctive sound, much different than the rifles either side of it on the capacity scale that burn the same powders.

There was a guy who used to shoot trap with us who would have, usually, one shell loaded with black powder every round of trap. It made a significantly different sound (as well as a big cloud of smoke.

It's not as simple as just muzzle pressure. Noise measurements are higher in the direction the barrel is pointing than from behind. Partly this is due to the angle the bullet's supersonic shock wave propagates. A German paper I found a while back points to pre-war modeling which assumes sound begins radiating once the front of a gas sphere formed by the muzzle exhaust slows to sub sonic. Said gas ball would be affected by charge weight, powder energy density and burning speed, expansion ratio, etc.

If your company or college has an ISO subscription, ISO CEN 17201-1 provides a way to estimate peak sound. I don't have access (too cheap to pay for it), but I'd be happy to read a copy you send me.

Hmm I was thinking of the barrel being a bell and pressure being how hard you strike it..
But the gas ball makes more sense...
After all a sonic boom is the air collapsing around where the plane was.
Right?



Interesting. So it is an oxygen limited exothermic reaction?

I should go back and read the quickload documentation for % charge consumed....

Smokeless powder is primarily cellulose, C6 H10 05, but in modern rifles pretty much burns up in the first few inches in front of the chamber. Or as I noted, all the powder that's going to burn will burn in that distance. How much burns (and how quickly) depends on the peak pressure, since progressive rifle powders are designed to burn most completely at a certain pressure.

IMR4895, for example, was designed to burn best at a slightly lower peak pressure than most newer powders, because it was primarily designed for the M-1 "Garand." Which is partly why a lot of older handloading information firmly stated the most accurate loads occurred at somewhat under "maximum" pressure: Hundreds of tons of the original military-surplus 4895 were used by a LOT of handloaders in the decades after WWII. Most of today's rifle powders, however, are designed to burn best at around 10,000 PSI more than IMR4895 (either the surplus powder, or today's newly produced IMR4895).

But with any of them, the oxygen content of the nitrocellulose is consumed long before the gas produced exits the muzzle. When the still very hot "oxygen-starved" gas exits, it re-ignites due to the fresh supply of oxygen. This produces muzzle flash, NOT still-burning powder granules.

This is exactly why my 1884 trapdoor Springfield .45-70 shoots very accurately with bullets in the 400-grain range and IMR-4895, yet results in a bunch of unburned granules, both in the barrel and out (which can be seen by laying a sheet on the ground in front of the muzzle). The pressure never gets anywhere near ideal for even IMR4895, but enough burns consistently to result in good accuracy. But despite that there's there's almost no muzzle flash, because the remaining powder granules are NOT burning--and the long barrel results in very little hot gas exiting the muzzle.

QL a computer simulation, which may or may not match reality, in varying degrees. This includes the percentage of powder burned.

I always thought that a shotgun had a hollow sound. I could hear the other hunters shooting across the valley on opening day for pheasants.

https://en.wikipedia.org/wiki/Helmholtz_resonance

http://hyperphysics.phy-astr.gsu.edu/hbase/Waves/cavity.html#c4

0.7" diameter = 0.5^2" area.
Barrel length = 36"
Volume = 18 ^3"
speed of sound = 343 m/s

Using this calculator and these assumptions, the average 12 ga barrel would have a resonance of 60 Hz.

For those of you in Rio Linda, it sounds like the milk jug band.