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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?


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


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Exit pressure relates to gas jet velocity.


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Like H335 in a 556 rifle,at night.

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

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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%).


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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.


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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.

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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


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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.

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Originally Posted by denton
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%).


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.

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


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Originally Posted by Filaman
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.


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

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Originally Posted by mathman
Originally Posted by Filaman
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.


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

It does when I fart.Loud and heavy recoil.


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


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.

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Originally Posted by Huntz
Originally Posted by mathman
Originally Posted by Filaman
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.


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

It does when I fart.Loud and heavy recoil.


Loud needs the atmosphere, recoil doesn't. grin

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Originally Posted by mathman
Originally Posted by Huntz
Originally Posted by mathman
Originally Posted by Filaman
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.


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

It does when I fart.Loud and heavy recoil.


Loud needs the atmosphere, recoil doesn't. grin



Yep😁 good way to put it.


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Originally Posted by Filaman
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.


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.



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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.


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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.
[Linked Image]

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.

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


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