Post by BozoWise on Oct 30, 2003 0:00:55 GMT -5
I thought this was a good bit of info on the Scirocco bullet
Consider a new bullet contour before switching cartridges.
By Rick Jamison
The buck you see in the accompanying photo was taken with the new Swift .277 130-grain Scirocco bullet fired from a .277 Jamison wildcat cartridge. This new bullet has a great shape and shoots flatter than anything going in a hunting bullet. I was hunting early last November with Lynn and Alvy Johnson (P.O. Box 416, Fredonia, AZ 86022) when we came across a heavy-horned mule deer. The Bushnell rangefinder indicated the departing buck was 327 yards away, and by the time I fired, the buck was probably 350 yards out.
The .277 Scirocco blasted out of the rifle's bore at about 3,180 fps and met the buck with enough energy to create a .58 caliber mushroom and still drive clear through to the hide on the far side. I found later that the bullet retained 96 percent of its original weight. The Scirocco has a bonded core that really sticks to the jacket and results in high weight retention for good penetration.
This streamlined bullet is one flat shooter. With the load I was using, the bullet is no more than four inches from the line of sight all the way out to 400 yards. The new Hornady SST fits into the same category as the Swift Scirocco when it comes to downrange figures, and the two run neck and neck in the ballistic coefficient category.
BRAGGING ON BC
Plastic-tipped bullets--introduced a few years back with the famous Nosler Ballistic Tip--have really improved bullet tip shape, ballistic coefficient and in-flight efficiency. But how important is ballistic coefficient? Let's take a look at some solid information.
When you come right down to it, there are two things a bullet must do at minimum to kill cleanly. It needs adequate velocity to initiate bullet expansion. The amount of impact velocity necessary for expansion depends on how a bullet is designed. Most common hunting bullets produce positive expansion at 2,000 fps impact velocity; you want a bullet to be going at least that fast when it strikes.
The other component to terminal effectiveness is energy. The bullet needs enough energy to produce ample penetration and tissue destruction. The amount of energy necessary is partially dependent on the size of the game. Most folks agree, for instance, that 1,000 ft.-lbs. is a good figure for deer, and a well-placed shot that hits a buck with this much energy will produce a clean kill.
Velocity and energy dissipate as a bullet travels downrange, and the really significant thing is that after a bullet leaves the muzzle, the amount of velocity and energy delivered downrange is totally dependent on the shape of the bullet. Most hunters overlook the significance of this, but it says a lot about the importance of BC. Let's look at a specific example. Suppose you pick a 130-grain bullet for the .270 Win. that has a ballistic coefficient of .350, and you start it out at 2,900 fps muzzle velocity. At this velocity, the bullet will be packing 2,427 ft.-lbs. of energy when it leaves the rifle's muzzle.
More than a ton of muzzle energy sounds as if it should be plenty for taking deer at any distance. Running the numbers shows us that the bullet's energy will have dropped to 1,000 ft.-lbs. by the time it reaches 425 yards, which is a lot farther than most of us would shoot at a deer. But take a look at downrange velocity. The bullet will have slowed down to our minimum impact velocity of about 2,000 fps by the time it gets to a little less than 350 yards. If you're hunting open-country mulies, for example, you don't want to be using a load that is running out of gas at the 350-yard mark.
Now, let's take the same load and bullet weight with the same muzzle velocity, but let's pick a more streamlined bullet--one with a BC of .450--and see how it compares. This sleeker bullet retains the 2,000 fps minimum velocity level clear out to 450 yards, 100 yards farther than the bullet with a .350 BC. We can also calculate that the minimum 1,000 ft.-lbs. of energy will be carried clear out to 525 yards with this sleek bullet, also 100 yards farther than the other bullet.
NO-COST IMPROVEMENT
As this example illustrates, we have added 100 yards of effective range to our deer load without changing anything but bullet shape. We have not added powder for increased pressure, muzzle blast and recoil. We have not needed a bigger cartridge and a new gun. We needed only a bullet with a better shape to improve load performance significantly.
The ballistic coefficients mentioned above are well within the range of BCs available in this bullet diameter. The amount of difference you see in a load is dependent upon the degree of change you make. If you switch from a bullet with a BC of .400 to one of .410, you're not going to see nearly as much difference. If you switch from a BC of .280 to one of .450, though, you're going to see a greater difference. The point is that BC does make a difference, and the new ultrasleek bullets can give you an undeniable advantage. (Reloaders should note that you have to seat these longer bullets a little deeper for the same overall cartridge length.)
If you want to improve the downrange effectiveness of your cartridge and load, you can do a lot simply by selecting a bullet with a streamlined shape. The downrange advantage to be gained in optimizing ballistic coefficient is really greater than the advantage that can be gained in adding powder to produce higher velocity. And by simply changing bullet shapes to improve downrange efficiency, you're not increasing muzzle blast, muzzle pressure or recoil--all of which have a tendency to reduce one's ability to shoot well.
Consider a new bullet contour before switching cartridges.
By Rick Jamison
The buck you see in the accompanying photo was taken with the new Swift .277 130-grain Scirocco bullet fired from a .277 Jamison wildcat cartridge. This new bullet has a great shape and shoots flatter than anything going in a hunting bullet. I was hunting early last November with Lynn and Alvy Johnson (P.O. Box 416, Fredonia, AZ 86022) when we came across a heavy-horned mule deer. The Bushnell rangefinder indicated the departing buck was 327 yards away, and by the time I fired, the buck was probably 350 yards out.
The .277 Scirocco blasted out of the rifle's bore at about 3,180 fps and met the buck with enough energy to create a .58 caliber mushroom and still drive clear through to the hide on the far side. I found later that the bullet retained 96 percent of its original weight. The Scirocco has a bonded core that really sticks to the jacket and results in high weight retention for good penetration.
This streamlined bullet is one flat shooter. With the load I was using, the bullet is no more than four inches from the line of sight all the way out to 400 yards. The new Hornady SST fits into the same category as the Swift Scirocco when it comes to downrange figures, and the two run neck and neck in the ballistic coefficient category.
BRAGGING ON BC
Plastic-tipped bullets--introduced a few years back with the famous Nosler Ballistic Tip--have really improved bullet tip shape, ballistic coefficient and in-flight efficiency. But how important is ballistic coefficient? Let's take a look at some solid information.
When you come right down to it, there are two things a bullet must do at minimum to kill cleanly. It needs adequate velocity to initiate bullet expansion. The amount of impact velocity necessary for expansion depends on how a bullet is designed. Most common hunting bullets produce positive expansion at 2,000 fps impact velocity; you want a bullet to be going at least that fast when it strikes.
The other component to terminal effectiveness is energy. The bullet needs enough energy to produce ample penetration and tissue destruction. The amount of energy necessary is partially dependent on the size of the game. Most folks agree, for instance, that 1,000 ft.-lbs. is a good figure for deer, and a well-placed shot that hits a buck with this much energy will produce a clean kill.
Velocity and energy dissipate as a bullet travels downrange, and the really significant thing is that after a bullet leaves the muzzle, the amount of velocity and energy delivered downrange is totally dependent on the shape of the bullet. Most hunters overlook the significance of this, but it says a lot about the importance of BC. Let's look at a specific example. Suppose you pick a 130-grain bullet for the .270 Win. that has a ballistic coefficient of .350, and you start it out at 2,900 fps muzzle velocity. At this velocity, the bullet will be packing 2,427 ft.-lbs. of energy when it leaves the rifle's muzzle.
More than a ton of muzzle energy sounds as if it should be plenty for taking deer at any distance. Running the numbers shows us that the bullet's energy will have dropped to 1,000 ft.-lbs. by the time it reaches 425 yards, which is a lot farther than most of us would shoot at a deer. But take a look at downrange velocity. The bullet will have slowed down to our minimum impact velocity of about 2,000 fps by the time it gets to a little less than 350 yards. If you're hunting open-country mulies, for example, you don't want to be using a load that is running out of gas at the 350-yard mark.
Now, let's take the same load and bullet weight with the same muzzle velocity, but let's pick a more streamlined bullet--one with a BC of .450--and see how it compares. This sleeker bullet retains the 2,000 fps minimum velocity level clear out to 450 yards, 100 yards farther than the bullet with a .350 BC. We can also calculate that the minimum 1,000 ft.-lbs. of energy will be carried clear out to 525 yards with this sleek bullet, also 100 yards farther than the other bullet.
NO-COST IMPROVEMENT
As this example illustrates, we have added 100 yards of effective range to our deer load without changing anything but bullet shape. We have not added powder for increased pressure, muzzle blast and recoil. We have not needed a bigger cartridge and a new gun. We needed only a bullet with a better shape to improve load performance significantly.
The ballistic coefficients mentioned above are well within the range of BCs available in this bullet diameter. The amount of difference you see in a load is dependent upon the degree of change you make. If you switch from a bullet with a BC of .400 to one of .410, you're not going to see nearly as much difference. If you switch from a BC of .280 to one of .450, though, you're going to see a greater difference. The point is that BC does make a difference, and the new ultrasleek bullets can give you an undeniable advantage. (Reloaders should note that you have to seat these longer bullets a little deeper for the same overall cartridge length.)
If you want to improve the downrange effectiveness of your cartridge and load, you can do a lot simply by selecting a bullet with a streamlined shape. The downrange advantage to be gained in optimizing ballistic coefficient is really greater than the advantage that can be gained in adding powder to produce higher velocity. And by simply changing bullet shapes to improve downrange efficiency, you're not increasing muzzle blast, muzzle pressure or recoil--all of which have a tendency to reduce one's ability to shoot well.