How much sound difference does a revolver's gap make?

D

Doyle

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Has anyone ever seen any measurements done on the relative sound levels of a given cartridge when shot from a revolver vs a totally closed-breech barrel (like Contender or Encore)? I'm just wondering how much of the sound actually "leaks" through the cylinder gap.
 
Hmmm

I don't see suppressors on revolvers much at all. That may be one of the reasons why.

I have also seen slide lock devices on suppressed semi auto guns.

The logic behind the slide lock is similar to that gap on the revolver, keep the breech closed to keep the sound "in"
 
Bart, that first link is a good study but it was done revolver vs semi-auto. Not exactly revolver vs closed breech because some of the sound will leak out when the auto cycles. Still, a good read though.
 
The sound of a gun shot isn't from the powder burning. It's from the displaced air going back into place after the bullet and gasses have passed. There is no "leaking" sound.
By the time a pistol cycles, the bullet and gasses are long gone. The action does not open with either still in the firearm. Hence, there is no pressure in the barrel.
A Contender works the same way any single shot firearm works. The bullet and gasses go out the muzzle, the air gets displaced then goes back and there is a sonic "boom".
 
Neither a 1911 firing standard .45 ACP ammunition nor an 1873 Colt SAA firing standard .45 Colt ammunition exceeds the speed of sound, so there is no sonic boom associated with firing either firearm. Despite the absence of a sonic boom, both create a significant sound pressure signature -- enough to be extremely painful to anyone in proximity to the firing who isn't wearing hearing protection.

In the case of a revolver, pressure escapes through the barrel-cylinder gap. We know this -- that's why it's desirable to keep the gap as tight as possible within functional parameters. If pressure escapes through that gap, it stands to reason that the pressure wave ahead of those escaping gasses generates sound. The issue is how to measure and quantify the level of the sound thus created.
 
Has anyone ever seen any measurements done on the relative sound levels of a given cartridge when shot from a revolver vs a totally closed-breech barrel (like Contender or Encore)? I'm just wondering how much of the sound actually "leaks" through the cylinder gap.
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The first sound we hear from a gun shot is the sound of the gas leaving the barrel from the bc gap in front of the bullet and from the muzzle. It is burning and expands in all directions very fast, this produces a sound. There is also a small amount that leaves the barrel from the barrel cylinder gap. The next sound is the gas leaving the barrel after the bullet leaves. This is the gas that pushes the bullet forward. That pressure will vary by load, powder, bullet, etc. This happens so fast that we hear it all as one sound.

This is all before the sound of the bullet breaking the sound barrier if it will do that.

Well how would you measure that and what would it tell ya?

The barrels would have to be of the same length. The bullet and the powder would have to be identical. Measuring the sound decibels would have to be done under identical conditions. So let's say we measure 10 rounds of Federal 158 gr. 38 Spl. lrn and we get an average of 4 decibels difference between a revolver with a 7"" barrel and a contender with a 7" barrel. OK good.

Then we do the same test with Winchester ammo, same weight bullet. The sound will likely be different by a bit. Different velocity, different powder, etc. maybe louder or softer. Go to another load. It will be different again by some amount.

Change the length of the barrel of the gun and it will be even more different.

So what would be learned?

Not much that you could do anything with I think.

tipoc
 
A sonic boom happens when all ammo fires in the earth's atmosphere. Its the sudden compressed air wave moving through the atmosphere at the speed of sound. Gas escapes behind the bullet well into the supersonic speeds

A silencer traps and slows down escaping gas rates from the muzzle so the pressure wave is greatly reduced. Centerfire rifle ammo's gas leaves over 5 to 6 thousand fps.
 
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Neither a 1911 firing standard .45 ACP ammunition nor an 1873 Colt SAA firing standard .45 Colt ammunition exceeds the speed of sound, so there is no sonic boom associated with firing either firearm.
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The bullet may be subsonic, but the propellant gas is moving at a faster speed, approximately 1.5 times the speed of the bullet. So there may be a sonic boom from the propellant gas, aka muzzle blast. The speed of the propellant gas is listed for various firearms in this SAAMI document on recoil.

Edit: I see Bart B beat me by one minute :) There may be some long barreled shotguns where the propellant gases exit at a subsonic speed, but I'd guess that the propellant gas from all single projectile smokeless powder firearms is supersonic.
 
I'm just wondering how much of the sound actually "leaks" through the cylinder gap.
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Not enough that you could hear the difference with what all else is going on.

Next question: If I hold my thumb up to the BC gap while firing what caliber, powder and or pressure will I have to shoot before it takes a piece of my thumb off?

tipoc
 
10,000 psi gas pressure at the muzzle can push a bullet out at 3000 fps.

It'll push the same volume of air and gas a heck of alot faster.

Thanks, lever gun fan, for posting the link to SAAMI's information.
 
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Mr. O'Heir makes some really bizarre statements, but the one above takes the cake.

I can assure you that the burning of gunpowder (the EXPLOSION!) does make quite a bit of sound.
 
I believe it was Mythbusters that also tackled this question, with a fake hand made of wood and hotdogs. They used several different calibers and held the "hand" up to the B/C gap using tape. Let's just say it got messy.
 
Aguila Blanca said:
Neither a 1911 firing standard .45 ACP ammunition nor an 1873 Colt SAA firing standard .45 Colt ammunition exceeds the speed of sound, so there is no sonic boom associated with firing either firearm. Despite the absence of a sonic boom, both create a significant sound pressure signature -- enough to be extremely painful to anyone in proximity to the firing who isn't wearing hearing protection.



In the case of a revolver, pressure escapes through the barrel-cylinder gap. We know this -- that's why it's desirable to keep the gap as tight as possible within functional parameters. If pressure escapes through that gap, it stands to reason that the pressure wave ahead of those escaping gasses generates sound. The issue is how to measure and quantify the level of the sound thus created.
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This and Bart B covered it

As to holding your fingers close to the gap, I’ve actually experimented with this using myself as the test subject (call me a mad scientist). I did this as i was experimenting with different grip styles for a thumb forward hold on a revolver. If the fingers are up to half an inch of the cylinder gap (but not closer) any caliber up to 44 mag will not cause any serious damage. Lower pressure calibers (22lr, 38 special) don’t really hurt at all. 357 mag and 44 mag at that distance (1/2 inch) feel like you tapped your finger pretty good with a hammer. Not full on hit it, just a hefty tap. I haven’t gone closer and don’t intend to.
So yeah I know first hand that there is a little bit of hype and urban myth around this issue.
When i was in high school i had a fire cracker explode while holding it between my thumb and index finger. My fingers were throbbing for a couple hours. I know of a guy who lost a couple fingers when a firecracker went off inside his closed fist. The difference is important.
I certainly wouldn’t wrap my hand around the cylinder gap as it would probably would badly hurt me. But having some fingers in the vicinity of the gap isn’t going to take a finger off.
As for mythbusters, my fingers are significantly more structurally strong than a hot dog, and can take a harder hit without long term damage. But that doesn’t mean i want them too. :)


Sent from my iPhone using Tapatalk
 
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Can't tell you what to do with your own fingers that's your business but I've seen some pics of some seriously damaged flesh from being too close to the cylinder gap.

I've personally seen a guy holding a .357 cradled in his palm when it accidently went off, it split his skin very nasty a couple inches long seem deep, but the blackness of the wound filled with powder granules made it difficult to tell.

Emergency room, cleaning, several stiches, great deal of pain. and painful for a couple months afterward.

Better also hope that revolver isn't spitting any lead or it will be even worse.

As to the sound, well sound is a funny thing. We can measure it in detail, quantify and qualify it but the ear hears what the ear hears. And what the ear hears is different, depending on where the ear is, in relation to the sound source and reflective materials.

We can set up an experiment and measure identical rounds with and without barrel cylinder gaps, and get different values, but I'm pretty confident the naked ear won't be able to tell the difference.

Pistols and revolvers firing the same round sound different to the shooter. My experience is the carbine is a little quieter. Do you think that the longer barrel and more complete combustion of the powder, creating even more gas, and higher velocity produce less sound at the muzzle?

Or perhaps its because the muzzle is a foot + further from your ears??
 
Now we know not to put your finger over the BC gap.

We've also learned to not put our ear close to the bc gap as well. Oh and keep both clear of the muzzle while firing.

I'm just wondering how much of the sound actually "leaks" through the cylinder gap.
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Probably enough to make ya wet.

But as was said before, the sound, like the amount of gas itself and it's speed, would vary greatly based on a number of differing factors. Those factors, combined with the difficulty of getting an accurate measurement of the sound, would likely not render any information that was useful for any particular purpose. So the best answer to your question is...some, some sound will leak out. How much, well a tiny portion of what comes from the muzzle.

It will be easier to calculate how much gas "leaks" from the BC gap then it would be to calculate the decibel level of the sound and it's duration.

Someone can work on this. Meanwhile keep your ear away from that area of the gun.

tipoc
 
Silenced Revolvers

All about silenced revolvers: https://www.thefirearmblog.com/blog/2016/06/15/why-cant-revolvers-be-suppressed-or-can-they/
And one of them, the 1851 Nagant, had a mechanism that when the hammer was cocked, it would move the cylinder forward to seal against the barrel/forcing cone. So it must have been thought of as significant enough to make a difference audibly.

From reading Kuhnhausen's manual on revolvers, if my memory serves, there's a diagram that surprised me which illustrates how a crooked cylinder can let more gas out of one side than the other. This jet-like action can push the gun in a certain direction throwing the aim off with every shot. That's a significant amount of gas in my mind.
 
My experience is the carbine is a little quieter. Do you think that the longer barrel and more complete combustion of the powder, creating even more gas, and higher velocity produce less sound at the muzzle?
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For a given cartridge, the gas pressure at the muzzle is typically lower for a longer barrel, and higher for a shorter barrel. So while the bullet velocity is higher, the carbine firing a pistol/revolver cartridge may have a lower sound contribution from the escaping gas than the shorter barreled pistol/revolver.
 
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