411man
01-01-2008, 03:06 AM
http://www.gunsandammomag.com/ammunition/subsonic_100507/index.html
fromGuns & Ammo
Super Subsonics
Slow down: For out-and-out accuracy, put away the high- and hyper-velocity ammo and load your favorite .22 with "below the speed of sound" stuff.
By John Haviland
This blue grouse was taken with a Remington Subsonic HP. The bullet didn't ruin a bite of meat.
Subsonic .22s are the loads to shoot for the best accuracy and meat-saving shots on small game. You might think high-velocity .22 Long Rifles, with a shorter time of flight, would drift less in the wind and be more accurate than subsonics. However, because subsonics are slightly slower than the speed of sound, they do not encounter a sharp increase in air resistance; that results in less wind drift and more stable flight.
A Not-So-Simple Explanation
The exact speed of sound depends on the temperature of the air. At sea level with a temperature of 70 degrees, sound travels at about 1,128 feet per second. As temperatures fall, air becomes denser and sound travels slower. When a bullet approaches and first passes this velocity, airflow severely buffets it. The outer edge of this transonic zone, if we go with the 1,128 fps at 70 degrees, is between about 902 and 1,466 fps.
Glen Weeks of Winchester Ammunition says a bullet that does not reach the speed of sound is much less affected by air turbulence. "A shadow graph of a subsonic bullet in flight shows a shock wave being pushed in front of the bullet and flowing around the bullet," Weeks says. "But as a bullet transitions from subsonic to supersonic, the shadow graph shows the bullet piercing the shock wave and the shock wave actually adhering somewhat to the bullet." Weeks says the shock wave created at these transonic velocities causes all sorts of turbulence. That turbulence can destabilize a bullet and throw it somewhat off course.
This transonic zone is about the speed of most high-velocity .22 Long Rifle bullets flying to out past 100 yards or so. A high-velocity .22 Long Rifle bullet leaves a rifle muzzle at the upper end of this zone, so it suffers little buffeting at its start. But somewhere around 75 yards the bullet has slowed enough that it is subject to the full pummeling of the increased air resistance at the speed of sound.
These three five-shot groups fired at 50 yards with Lapua subsonic hollowpoints averaged .35 inch. In terms of accuracy, subsonic ammo is the way to go.
Now for the complicated part. Even though a subsonic bullet starts out several hundred fps slower than a high-velocity one, the subsonic drifts less in the wind. Logic dictates that the high-speed bullet should drift less because it has a shorter time of flight and thus wind has less time to push it off course. But that is not the case.
Allan Jones of CCI and Speer Bullets thinks subsonic bullets drift less in the wind than supersonic projectiles because of the characteristics of airflow.
A hollowpoint helps .22 bullets expand, even though they are flying slower than the speed of sound. On the left is a CCI subsonic HP bullet recovered from a Ballistic Technology Test Tube. On the right is a Winchester Power Point bullet that had a muzzle velocity of 1,303 fps.
"At subsonic speeds, the flow of air is detached from the bullet and more easily moves away from the bullet and that doesn't restrain the bullet as much," Jones says. That lower resistance gives a bullet a slightly higher ballistic coefficient compared to when it's going through the increased drag of the transonic zone.
When a bullet goes through the transonic zone, an increased amount of energy is required to push the shock waves. "When the bullet's going through the transonic zone, air compresses ahead of it and shock waves form up at different places on the bullet. This buffets the bullet and causes some loss of velocity and degrades the ballistic coefficient," Jones says.
fromGuns & Ammo
Super Subsonics
According to Robert Rinker's Understanding Firearm Ballistics, wind deflection of .22 Long Rifle bullets is "not controlled by time of flight but by the loss of velocity during time of flight. During the transition velocity range above the speed of sound, the drag increases disproportionately higher than the velocity increases. In other words, if the velocity is increased by a small amount, the drag increases by a large amount. This situation is unique to this velocity range [1,000 to 1,350 fps]," Rinker writes.
Small-game stopper: A hollowpoint helps subsonic .22 bullets expand. The CCI subsonic HP (left) and the CCI Select solidpoint (right) were recovered from a Ballistic Technology Test Tube.
An example of what Jones and Rinker stated is reflected in the ballistics of two loads taken from Bob Forker's Ammo & Ballistics for Hunters, Shooters and Collectors . Forker compares the ballistics of a CCI Velocitor 40-grain HP (BC .141, MV 1,435 fps) with a Lapua 40-grain Master M (BC .132, MV 1,066 fps). With a 10-mph wind-drift factor, the fast CCI load drifts 1.4 inches at 50 yards (1,249 fps), 3.1 inches at 75 yards (1,174 fps) and 5.4 inches at 100 yards (1,112 fps).
The Lapua load drifts 1.1 inches at 50 yards (981 fps), 2.4 inches at 75 yards (947 fps) and 4.3 inches at 100 yards (917 fps).
The Velocitor and Lapua bullets are the same weight and quite close in their ballistic coefficients. The percentage of retained muzzle velocity at 100 yards shows that the slower Lapua has retained nearly as much of its muzzle velocity (86 percent) as the Velocitor bullet did at 50 yards (87 percent).
ACCURACY RESULTS
LOAD BULLET WEIGHT (gr.) AVG. VELOCITY (fps) AVG. GROUP (in.)
CCI Subsonic HP 40 1,040 .91
CCI Green Tag Solid 40 1,058 .62
Lapua Subsonic HP 36 1,016 .35
Lapua Midas M Solid 40 1,078 .49
Lapua Scoremax Solid 48 1,007 .46
Remington Subsonic HP 38 1,055 .72
Remington/Eley Club Xtra Solid 40 1,016 .59
CCI Mini Mag HP 36 1,298 .87
CCI Select Solid 40 1,185 .55
Remington Yellow Jacket HP 33 1,368 .80
Winchester Power Point HP 40 1,303 .49
Rifle used was a Ruger 10/22 with an 18 3/4 inch Volquartsen barrel. Groups were the average of three five-shot groups at 50 yards
I've shot the Lapua Subsonic HP load in my Ruger 10/22 wearing a Volquartsen stainless steel bull barrel for years at a local turkey shoot. The combination's accuracy gives my cousin fits of anguish. Gene shows up every year at the turkey shoot with a Winchester Model 52 that, by all rights, should clean the clock of my Ruger 10/22. But the ammunition Gene shoots is whatever happens to be on the dash of his pickup at the time--usually high-velocity hollowpoints.
Those shells will never be as accurate as the Lapua Subsonic HP cartridges. For one thing, the Lapua rounds are handled carefully during production and packaged securely so that the soft lead bullets remain fully formed and free of dents and dings. A nick or scratch on the heel of a .22 bullet can set the bullet off balance or allow powder gas to jet up the side of it and ruin accuracy.
At the turkey shoot, 10 contestants each fire one shot at 50 yards at one of 10 one-inch circles. The shooter with a bullet closest to the center of a circle wins a frozen turkey. This is devilishly simple--no sighting shots to dope the wind or group to win with an average. Just make your best estimate, and put it all on one bullet.
As the accuracy chart shows, on a fairly calm morning the Lapua Subsonic HP averaged .35-inch groups for three five-shot groups at 50 yards from my 10/22. That accuracy usually keeps me in the running for a turkey if I do my part.
fromGuns & Ammo
Super Subsonics
The problem arises when the wind rears its ugly head. At the turkey shoot, the wind comes from the right and often from the right and behind. With the target positioned above the bench on a sloping hill, the wind drifts the bullet not only to the left but up a slight amount. The subsonic bullet drifts a few tenths of an inch less than high-velocity bullets in a 10-mph wind at 50 yards. But often that's the deciding factor.
This lineup of subsonic .22 Long Rifle loads used by the author indicates that there's no shortage of brands and types to choose from.
The advantage of subsonic over high-velocity .22s may be difficult to distinguish in a garden-variety rifle. However, it is apparent in a target rifle, and that's why .22 match competitors shoot subsonic ammo.
Small Game
I asked a friend of mine in Indiana what .22 rimfire loads he uses when he hunts fox squirrels.
"I always shoot them in the head," he says. "It doesn't matter what load you use because if you shoot them through the shoulders or along the back it ruins a lot of meat." So he uses the most accurate load he can find. Often that's a subsonic load.
I've used .22s to shoot grouse. Some of my friends head-shoot them, but I'm not that good offhand. Instead I shoot for the base of the neck or the wing butts. The grouse beat their wings for a few seconds with a bullet through the neck or usually just fall over dead with a bullet through the wing butts. However, a high-velocity .22 creates bloodshot meat with those shot placements.
Last fall I spent a few days hunting bighorn sheep and shot ruffed grouse to liven up the taste of my canned chicken stew. Remington Subsonic HPs poked a hole clear through the wing butts of the grouse, and they fell dead right on the spot. None of them had so much as a bite of bloodshot meat.
TEST TUBE RESULTS
LOAD (gr.) BULLET WEIGHT (gr.) MUZZLE VELOCITY (fps) PENETRATION (in.) EXPANDED DIAMETER WEIGHT RETENTION
CCI Subsonic HP 40
1,040
1.5.41340CCI Select Solid 40401,1852.5.26040Lapua Subsonic HP361,0163.25.24036
From the 25-inch barrel of my CZ 452, the report was so mild that other grouse in the covey never even turned their heads toward the noise.
According to Allan Jones, the .22 Long Rifle subsonic hollowpoint load was first developed for shooting rabbits in Australia. "These shooters wanted a quiet load that didn't have the crack of a supersonic bullet that scared the rabbits," Jones says.The lighter amount of propellant contained in subsonic loads also lessens their report.
To test the penetration and expansion of bullets of various .22 Long Rifle loads, I shot the bullets of five loads of various velocities and bullet styles into Ballistic Technology Bullet Test Tubes (see chart). All of the bullets made a wound channel through the material about the width of a No. 2 pencil. The CCI Subsonic HP and the Winchester Power Points, though, expanded broadly, with the nose of their bullets peeling back to the base of the bullets. On the other hand, the Lapua and Remington subsonic loads provided deep penetration.
The obvious conclusion? Subsonics are unsurpassed for accuracy and, with the right load, for small game.
fromGuns & Ammo
Super Subsonics
Slow down: For out-and-out accuracy, put away the high- and hyper-velocity ammo and load your favorite .22 with "below the speed of sound" stuff.
By John Haviland
This blue grouse was taken with a Remington Subsonic HP. The bullet didn't ruin a bite of meat.
Subsonic .22s are the loads to shoot for the best accuracy and meat-saving shots on small game. You might think high-velocity .22 Long Rifles, with a shorter time of flight, would drift less in the wind and be more accurate than subsonics. However, because subsonics are slightly slower than the speed of sound, they do not encounter a sharp increase in air resistance; that results in less wind drift and more stable flight.
A Not-So-Simple Explanation
The exact speed of sound depends on the temperature of the air. At sea level with a temperature of 70 degrees, sound travels at about 1,128 feet per second. As temperatures fall, air becomes denser and sound travels slower. When a bullet approaches and first passes this velocity, airflow severely buffets it. The outer edge of this transonic zone, if we go with the 1,128 fps at 70 degrees, is between about 902 and 1,466 fps.
Glen Weeks of Winchester Ammunition says a bullet that does not reach the speed of sound is much less affected by air turbulence. "A shadow graph of a subsonic bullet in flight shows a shock wave being pushed in front of the bullet and flowing around the bullet," Weeks says. "But as a bullet transitions from subsonic to supersonic, the shadow graph shows the bullet piercing the shock wave and the shock wave actually adhering somewhat to the bullet." Weeks says the shock wave created at these transonic velocities causes all sorts of turbulence. That turbulence can destabilize a bullet and throw it somewhat off course.
This transonic zone is about the speed of most high-velocity .22 Long Rifle bullets flying to out past 100 yards or so. A high-velocity .22 Long Rifle bullet leaves a rifle muzzle at the upper end of this zone, so it suffers little buffeting at its start. But somewhere around 75 yards the bullet has slowed enough that it is subject to the full pummeling of the increased air resistance at the speed of sound.
These three five-shot groups fired at 50 yards with Lapua subsonic hollowpoints averaged .35 inch. In terms of accuracy, subsonic ammo is the way to go.
Now for the complicated part. Even though a subsonic bullet starts out several hundred fps slower than a high-velocity one, the subsonic drifts less in the wind. Logic dictates that the high-speed bullet should drift less because it has a shorter time of flight and thus wind has less time to push it off course. But that is not the case.
Allan Jones of CCI and Speer Bullets thinks subsonic bullets drift less in the wind than supersonic projectiles because of the characteristics of airflow.
A hollowpoint helps .22 bullets expand, even though they are flying slower than the speed of sound. On the left is a CCI subsonic HP bullet recovered from a Ballistic Technology Test Tube. On the right is a Winchester Power Point bullet that had a muzzle velocity of 1,303 fps.
"At subsonic speeds, the flow of air is detached from the bullet and more easily moves away from the bullet and that doesn't restrain the bullet as much," Jones says. That lower resistance gives a bullet a slightly higher ballistic coefficient compared to when it's going through the increased drag of the transonic zone.
When a bullet goes through the transonic zone, an increased amount of energy is required to push the shock waves. "When the bullet's going through the transonic zone, air compresses ahead of it and shock waves form up at different places on the bullet. This buffets the bullet and causes some loss of velocity and degrades the ballistic coefficient," Jones says.
fromGuns & Ammo
Super Subsonics
According to Robert Rinker's Understanding Firearm Ballistics, wind deflection of .22 Long Rifle bullets is "not controlled by time of flight but by the loss of velocity during time of flight. During the transition velocity range above the speed of sound, the drag increases disproportionately higher than the velocity increases. In other words, if the velocity is increased by a small amount, the drag increases by a large amount. This situation is unique to this velocity range [1,000 to 1,350 fps]," Rinker writes.
Small-game stopper: A hollowpoint helps subsonic .22 bullets expand. The CCI subsonic HP (left) and the CCI Select solidpoint (right) were recovered from a Ballistic Technology Test Tube.
An example of what Jones and Rinker stated is reflected in the ballistics of two loads taken from Bob Forker's Ammo & Ballistics for Hunters, Shooters and Collectors . Forker compares the ballistics of a CCI Velocitor 40-grain HP (BC .141, MV 1,435 fps) with a Lapua 40-grain Master M (BC .132, MV 1,066 fps). With a 10-mph wind-drift factor, the fast CCI load drifts 1.4 inches at 50 yards (1,249 fps), 3.1 inches at 75 yards (1,174 fps) and 5.4 inches at 100 yards (1,112 fps).
The Lapua load drifts 1.1 inches at 50 yards (981 fps), 2.4 inches at 75 yards (947 fps) and 4.3 inches at 100 yards (917 fps).
The Velocitor and Lapua bullets are the same weight and quite close in their ballistic coefficients. The percentage of retained muzzle velocity at 100 yards shows that the slower Lapua has retained nearly as much of its muzzle velocity (86 percent) as the Velocitor bullet did at 50 yards (87 percent).
ACCURACY RESULTS
LOAD BULLET WEIGHT (gr.) AVG. VELOCITY (fps) AVG. GROUP (in.)
CCI Subsonic HP 40 1,040 .91
CCI Green Tag Solid 40 1,058 .62
Lapua Subsonic HP 36 1,016 .35
Lapua Midas M Solid 40 1,078 .49
Lapua Scoremax Solid 48 1,007 .46
Remington Subsonic HP 38 1,055 .72
Remington/Eley Club Xtra Solid 40 1,016 .59
CCI Mini Mag HP 36 1,298 .87
CCI Select Solid 40 1,185 .55
Remington Yellow Jacket HP 33 1,368 .80
Winchester Power Point HP 40 1,303 .49
Rifle used was a Ruger 10/22 with an 18 3/4 inch Volquartsen barrel. Groups were the average of three five-shot groups at 50 yards
I've shot the Lapua Subsonic HP load in my Ruger 10/22 wearing a Volquartsen stainless steel bull barrel for years at a local turkey shoot. The combination's accuracy gives my cousin fits of anguish. Gene shows up every year at the turkey shoot with a Winchester Model 52 that, by all rights, should clean the clock of my Ruger 10/22. But the ammunition Gene shoots is whatever happens to be on the dash of his pickup at the time--usually high-velocity hollowpoints.
Those shells will never be as accurate as the Lapua Subsonic HP cartridges. For one thing, the Lapua rounds are handled carefully during production and packaged securely so that the soft lead bullets remain fully formed and free of dents and dings. A nick or scratch on the heel of a .22 bullet can set the bullet off balance or allow powder gas to jet up the side of it and ruin accuracy.
At the turkey shoot, 10 contestants each fire one shot at 50 yards at one of 10 one-inch circles. The shooter with a bullet closest to the center of a circle wins a frozen turkey. This is devilishly simple--no sighting shots to dope the wind or group to win with an average. Just make your best estimate, and put it all on one bullet.
As the accuracy chart shows, on a fairly calm morning the Lapua Subsonic HP averaged .35-inch groups for three five-shot groups at 50 yards from my 10/22. That accuracy usually keeps me in the running for a turkey if I do my part.
fromGuns & Ammo
Super Subsonics
The problem arises when the wind rears its ugly head. At the turkey shoot, the wind comes from the right and often from the right and behind. With the target positioned above the bench on a sloping hill, the wind drifts the bullet not only to the left but up a slight amount. The subsonic bullet drifts a few tenths of an inch less than high-velocity bullets in a 10-mph wind at 50 yards. But often that's the deciding factor.
This lineup of subsonic .22 Long Rifle loads used by the author indicates that there's no shortage of brands and types to choose from.
The advantage of subsonic over high-velocity .22s may be difficult to distinguish in a garden-variety rifle. However, it is apparent in a target rifle, and that's why .22 match competitors shoot subsonic ammo.
Small Game
I asked a friend of mine in Indiana what .22 rimfire loads he uses when he hunts fox squirrels.
"I always shoot them in the head," he says. "It doesn't matter what load you use because if you shoot them through the shoulders or along the back it ruins a lot of meat." So he uses the most accurate load he can find. Often that's a subsonic load.
I've used .22s to shoot grouse. Some of my friends head-shoot them, but I'm not that good offhand. Instead I shoot for the base of the neck or the wing butts. The grouse beat their wings for a few seconds with a bullet through the neck or usually just fall over dead with a bullet through the wing butts. However, a high-velocity .22 creates bloodshot meat with those shot placements.
Last fall I spent a few days hunting bighorn sheep and shot ruffed grouse to liven up the taste of my canned chicken stew. Remington Subsonic HPs poked a hole clear through the wing butts of the grouse, and they fell dead right on the spot. None of them had so much as a bite of bloodshot meat.
TEST TUBE RESULTS
LOAD (gr.) BULLET WEIGHT (gr.) MUZZLE VELOCITY (fps) PENETRATION (in.) EXPANDED DIAMETER WEIGHT RETENTION
CCI Subsonic HP 40
1,040
1.5.41340CCI Select Solid 40401,1852.5.26040Lapua Subsonic HP361,0163.25.24036
From the 25-inch barrel of my CZ 452, the report was so mild that other grouse in the covey never even turned their heads toward the noise.
According to Allan Jones, the .22 Long Rifle subsonic hollowpoint load was first developed for shooting rabbits in Australia. "These shooters wanted a quiet load that didn't have the crack of a supersonic bullet that scared the rabbits," Jones says.The lighter amount of propellant contained in subsonic loads also lessens their report.
To test the penetration and expansion of bullets of various .22 Long Rifle loads, I shot the bullets of five loads of various velocities and bullet styles into Ballistic Technology Bullet Test Tubes (see chart). All of the bullets made a wound channel through the material about the width of a No. 2 pencil. The CCI Subsonic HP and the Winchester Power Points, though, expanded broadly, with the nose of their bullets peeling back to the base of the bullets. On the other hand, the Lapua and Remington subsonic loads provided deep penetration.
The obvious conclusion? Subsonics are unsurpassed for accuracy and, with the right load, for small game.