Could someone please explain the benefits of subsonic rounds...
- Thread starter lord-humungous
- Start date
stormbringer
CGN Ultra frequent flyer
- Location
- S.W. Ontario
They are quiet..........
Most match ammo is subsonic, to improve accuracy.
Bullets slow down as they proceed downrange due to friction with the air. Unlike centerfire ammo, most high velocity rimfire ammo has a muzzle velocity just a few hundred feet/sec above the speed of sound. It slows below the speed of sound within 50 yards of exiting the muzzle. Hyper velocity .22 ammo is faster but also slows down quicker because the bullets tend to be lighter and have less momentum.
A bullet which exits the muzzle faster than the speed of sound makes a CRACK sound as it slows below the speed of sound and breaks the sound barrier (or transsonic barrier). Its kind of like the sonic boom from a supersonic jet slowing below mach one. That's why a rimfire round fired into the ground at your feet is pretty quiet, it stays supersonic until it is in the ground.
When the bullet passes from supersonic to subsonic in the air it can also become unstable:the forces which make that CRACK can affect the flight of the bullet. Subsonic bullets do not traverse the sound barrier while in flight and are therefore more stable, and more accurate in many instaces.
High velocity ammo can be just as accurate or even more accurate than subsonic at shorter distances if the bullet is still travelleing faster than the speed of sound when it hits the target. Thats one reason why many people shoot great groups with cheap ammo at 20 yards, decent groups at 50, and can't hit anything at 100.
Bullets slow down as they proceed downrange due to friction with the air. Unlike centerfire ammo, most high velocity rimfire ammo has a muzzle velocity just a few hundred feet/sec above the speed of sound. It slows below the speed of sound within 50 yards of exiting the muzzle. Hyper velocity .22 ammo is faster but also slows down quicker because the bullets tend to be lighter and have less momentum.
A bullet which exits the muzzle faster than the speed of sound makes a CRACK sound as it slows below the speed of sound and breaks the sound barrier (or transsonic barrier). Its kind of like the sonic boom from a supersonic jet slowing below mach one. That's why a rimfire round fired into the ground at your feet is pretty quiet, it stays supersonic until it is in the ground.
When the bullet passes from supersonic to subsonic in the air it can also become unstable:the forces which make that CRACK can affect the flight of the bullet. Subsonic bullets do not traverse the sound barrier while in flight and are therefore more stable, and more accurate in many instaces.
High velocity ammo can be just as accurate or even more accurate than subsonic at shorter distances if the bullet is still travelleing faster than the speed of sound when it hits the target. Thats one reason why many people shoot great groups with cheap ammo at 20 yards, decent groups at 50, and can't hit anything at 100.
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i hope to conclude my testing of the .300 Whisper with cast bullets soon and hope to report on the theory of reduced vel. loss (percentage) when weather permits me to open my unlimited distance range. So far the <1100 fps. loads have shown great accuracy, next i will load 'em up to 1800fps and check for accuracy and drop.(not just what the mags. say)
I made some sub sonic 30-30;s using a cast bullet. They are nice and quiet, good for dispatching varmits out the bedroom window without blowing out your ears
Yeah I've done the same with 30-30, .303 and 7.62x54R using cast bullets and pistol powders most of the gas is low pressure when the bullet leaves the barrel so they are quite quiet yet still have the power and penetration to take even a deer at close range. I estimate that these 150gr bullets have about 300 ft/lbs.
