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Old October 21, 2002, 11:04 PM   #1
FlyboyAZ
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subsonic handgun rounds

Does anyone have experience with subsonic handgun rounds? Anything below about 1100 fps is pretty much subsonic. What I would like to know is how much noise these rounds make. There is still the expanding gas issue but are these relatively quiet when coming out of a 6in revolver? The Hornady manual I am using shows various grain bullets going down to 700 fps for a 357. Is the accuracy incredibly poor at this speed?

Just some things to chew on. Once I have my bench put together in the next week I will be working with some different ideas. Thanks for the time.
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Old October 22, 2002, 01:11 AM   #2
sricciardelli
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Tons of experience with subsonic handgun loads...it's called the .45ACP...
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Old October 22, 2002, 10:47 PM   #3
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to find out if Steve is correct, try one round of .45acp without ear protection. naah, don't do it. permanent ear damage. get a buddy to pop one off with you a block away. should satisfy one part of your experiment.

old target load for .45acp is 3.5 gr. bullseye w/185 grain bullet. kinda slow, but very accurate. still noisy.
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Old October 22, 2002, 10:50 PM   #4
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Velocity isn't everything as far as noise goes. Proximity of muzzle to ear, volume of gas pushed out the front and the diameter of the muzzle are all important factors.
The .45 is slow, but NOT quiet. Ditto the .38 and .44 Specials.
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Old October 23, 2002, 12:55 AM   #5
sricciardelli
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Subsonic refers to the speed of the bullet, not the explosive sound of detonation. There is a difference...
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Old October 23, 2002, 08:27 AM   #6
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there is some reading material available, if you do a good search, on low noise loads with smokeless powder. have never tried this myself. if the exit velocity of the bullet be subsonic (thus no shock wave) the other noise component to deal with is explosive pressure of gas leaving behind bullet. To minimize this, the pressure in the barrel (relative to atmospheric pressure) should be as low as possible. to do this you would want:

..a long barrel. this allows the pressure to build, getting the bullet up to some reasonable speed, peak early, and then decrease the rest of the way down the barrel (evan while the bullet may continue to accelerate). long (like 26 inches) kinda leaves handguns (subject of yr post) out.

..a spherical projectile of diameter at or evan a bit less than the lands. the shape and diameter are for minimum contact with the barrel, thus minimum resistance to acceleration of the projectile. buckshot (or possibly muzzle loading balls) are used. suitable wadding behind the projectile or sealant around it (instead of crimp) may reduce gas leakage.

..a relatively fast (i may have it wrong here) powder. the combustion and pressure peak occurr early; velocity and pressure profiles for the remainder of the ride in the barrel are more uniform among samples from a particular load lot.

be safe, and don't back off the powder load too much else you get the projectile stuck in the barrel.
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Old October 23, 2002, 10:36 AM   #7
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I fear there's a minor, and common, misconception - - -

With all respect, shu--

Using conventional ammunition, when pressure peaks, the bullet is going as fast as it will go. Your statement about longer barrel contributing to less-noisy shooting is true, to an extent. If all the powder is burned within the barrel and bullet exits muzzle immediately thereafter, this is just about peak efficiency for that load/gun combo. It CAN be quieter, but this is often a function of a supersonic bullet being slowed to subsonic velocity by a long barrel.

For instance, say a bullet from a warmish .22 LR cartridge chronographs at 1200 from a 7-/12 inch barrel, the pressure might well peak out at around the 12-inch point in a rifle barrel. From that point onward, the pressure is dropping, and the bullet is slowing, due to barrel friction. By the time it exits an 18-inch barrel, the bullet is kinda trans-sonic, and if fired in a 22 or 24-inch barrel, it will probably be traveling well under the speed of sound (subsonic.) This means you will not encounter the supersonic CRACK of the bullet’s passage through the air you would have had a few inches earlier. There will still be noise generated by the energy exiting the muzzle behind the bullet, of course.

I mentioned “conventional ammunition” above. The only hand-held weapons differing from this I can think of are the now-defunct Gyrojet, which actually launches (launched?) small rockets, which I am told, continued to accelerate after leaving the “muzzle,” due to the little rocket motor continuing to burn for several feet. Other examples include the Rocket Propelled Grenade (RPG,) the bazooka, and the Light Antitank Weapon (LAW) military munitions.

Best,
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Old October 23, 2002, 12:56 PM   #8
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Empirical info....
Aguilla subsonic .22 in different flavors.

From rifle.....very quiet, good enough for yard work.

From Ruger MKII and Smith K-22....loud enough to draw the law.

Sam
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Old October 23, 2002, 01:34 PM   #9
shu
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It may well be that maximum efficiency is achieved if pressure peaks and combustion is completed just as the projectile exits the barrel. What is asked for here however is not maximum efficiency but minimum noise.

Clearly the projectile can accelerate evan as pressure behind it decreases. This happens every time an air gun is fired.

My grasp of thermodynamics, scarcely adequate at its best to model evan the simple firing of an airgun, has long lain dormant. However..

..if pressure behind projectile is above atmospheric, there is a force behind the projectile equal to the pressure difference times cross sectional area;

..if this force is less than friction between projectile and barrel, the projectile will accelerate.

Under the right conditions I think the velocity of the projectile could continue to increase right up to the moment of exit from the barrel, but driving pressure decrease at that point to just above atmospheric. No expanding gas behind the bullet; no noise of expanding gas.

Practically however a handgun barrel just is not long enough to achieve a useful velocity.
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Old October 23, 2002, 11:45 PM   #10
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Thanks but no thanks

Well it sounds like I will never find what I want; a quiet 357 load for plinking. I do have a better understanding of the factors involved though so thanks for the input. I may dable with light rifle loads but I won't wast time with the handguns. I will have to check out the Aguila .22 for rifle work. Might be fun to play with.

Thanks again.
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Old October 24, 2002, 10:28 AM   #11
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Sam a .22 CB Short is the same way................in a bolt rifle with a 24" bbl. it's whisper quiet..............in my High Standard 5" Tournament Model it wakes up the neighborhood!
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Old October 24, 2002, 01:11 PM   #12
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Carlyle...
Thanks, I knew that and forgot about them.

Sam
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Old November 24, 2002, 04:27 PM   #13
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"Empirical info....
Aguilla subsonic .22 in different flavors.

From rifle.....very quiet, good enough for yard work.

From Ruger MKII and Smith K-22....loud enough to draw the law."

To add my observations along the same lines as the above . . .

Aguilla Colibri .22lr is completely silent out of an 18" barrel Browning BL-22 rifle. You only hear the little bullet slap a tree or rock. Makes less noise than my .22 Daisy air rifle.

But from a S&W 422 4" barrel auto pistol, you know a gun has been fired. Even with that Colibri.
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Old November 25, 2002, 12:46 AM   #14
C.R.Sam
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Have problem with the notion that bullet decelerates after pressure has peaked.

Extreme example of the converse would be gas powered air gun. Max pressure as projectile starts to move, pressure decreases from max while projectile accelerates.

As long as the pressure available is greater than that required to accelerate the projectile, the projectile will accelerate. This required pressure may be far below the peak pressure.

Sam
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Old November 25, 2002, 09:23 AM   #15
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You are correct Sam.

Look at it this way, in a 30-06 the perssure peak is around 48,000 CUP. This is attained at, and just past, the bullet being engraved at the leade.

By the time the bullet has traveled 12 inches or so the pressure is dropping. At the gas port on a Garand the pressure is around 10,000 CUP.

Take my word for it 10,000 CUP behind a bullet will still accelerate it even though it is a lot less than peak pressure.

IIRC a 16" barrel is optimum for a .22 LR. I am guessing that at that length the friction of the bullet in the barrel is then above the force of the hot gases needed to accelerate the bullet.
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Old November 25, 2002, 09:21 PM   #16
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Something to try

I've been searching for a nearly silent plinking load too.

The best I've done so far is using 95gr. .380acp (.355dia) lead bullets in .38spl cases over .5gr. bullseye.

They're a little quieter than the colibris out of a 4" pistol barrel.

I don't have a chrono so I can't tell how slow they're going but I can see them fly through the air.

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Old November 25, 2002, 11:35 PM   #17
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I've played around with Speer's round ball (cal = ?) in .44 special cases. Speer used to have data in their manual - maybe still do.

Essentially a better wrist rocket far as velocity goes. Wouldn't penetrate 1/4" plywood at (mumble) feet. Goodly dent & comes back pretty quick. Pretty quiet.

Far as .38 goes, I'd think a HBWC with a pinch o' bullseye would start you off. Start low, work up.

I've a 45Colt barrel for a Contender that I will play with some once I get the dies, etc. Nice tight closed breach. Ought to be a dandy platform for quiet on up.
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Old November 26, 2002, 02:31 PM   #18
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Hollow base wadcutters can be use in both .38 special (at about 750 fps) and in the .357 Magnum (at about 950fps).
I shot some in .38spl this weekend out of a 6 inch S&W 686. With earmuffs at the range or outside it sounds like barely a pop. Without ear protection it is quite loud and definitely needs ear protection.
Super colibris out of a 22 rifle are quieter than a pellet gun.
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