M
max.burgess
Guest
I just got a box of Berger Bullets and on the label it said g7 bc= .249 and below that it said g1 bc=.486. How can bullet have two bc's.
Thanks Max
Thanks Max
Ok...... just remember YOU DID ASK 
BC stands for Ballistic Coefficient.
"Coefficient" is kindofa' fancy way of saying "comparison."
Here's what they did, they fired a Big Ol' 50 caliber projectile weighing like 750 grains and took a bunch of measures off it.
They assigned it a value of '1'
they called it "G1 BC"
So now if they fire another bullet and compare it (coefficient) if it flies "just as good as" the 50cal they'll assign it a BC of 1.00
But most bullets don't, so they're a small fraction of '1'
but the world is infested with keyboard shooters, number crunchers, statisticians and wannabe's who think it ain't FAIR that alla' these bullets are acting so shamefully so they dreamt up ANOTHER bullet to use for the coefficient. They used a democrat tactic......saying "this bullet more closely "represents"......
etc
etc
etc
It's not much more twisted than considering SD to be more important than ES but basically it's just another way to express EXACTLY THE SAME THING!
coefficients, "assigned numbers," they're fun but confusing.
confusingexplanationsby
lol
al
BC stands for Ballistic Coefficient.
"Coefficient" is kindofa' fancy way of saying "comparison."
Here's what they did, they fired a Big Ol' 50 caliber projectile weighing like 750 grains and took a bunch of measures off it.
They assigned it a value of '1'
they called it "G1 BC"
So now if they fire another bullet and compare it (coefficient) if it flies "just as good as" the 50cal they'll assign it a BC of 1.00
But most bullets don't, so they're a small fraction of '1'
but the world is infested with keyboard shooters, number crunchers, statisticians and wannabe's who think it ain't FAIR that alla' these bullets are acting so shamefully so they dreamt up ANOTHER bullet to use for the coefficient. They used a democrat tactic......saying "this bullet more closely "represents"......
etc
etc
etc
It's not much more twisted than considering SD to be more important than ES but basically it's just another way to express EXACTLY THE SAME THING!
coefficients, "assigned numbers," they're fun but confusing.
confusingexplanationsby
lol
al
M
max.burgess
Guest
I've seen the bc in manuals and on boxes of bullets and I've seen sd but I've never seen 2 bc's on the same bullet.
Thanks Max
Thanks Max
H
Hombre0321
Guest
To date, the ‘standard projectile’ used to define BCs for the entire sporting arms industry is the G1 standard projectile. The G1 standard projectile which has a short nose, flat base, and bears more resemblance to a pistol bullet or an old unjacketed lead black powder cartridge rifle bullet than to a modern long range rifle bullet.
Thus with the G1 "standard projectle with its short nose and flat base is not a good indicator of the more modern "Long Range Bullet" whose profile is complettly different with its Spitzer type nose and boat Tailed rear. So for the G7 standared they used a bullet profile that more closely reflects the Long Range bullets thast are commonly used to day ie: HPBT
Another words there are two competely different bullet "Profiles that the G1 BC and the G7 BC are based on.
Roland
Thus with the G1 "standard projectle with its short nose and flat base is not a good indicator of the more modern "Long Range Bullet" whose profile is complettly different with its Spitzer type nose and boat Tailed rear. So for the G7 standared they used a bullet profile that more closely reflects the Long Range bullets thast are commonly used to day ie: HPBT
Another words there are two competely different bullet "Profiles that the G1 BC and the G7 BC are based on.
Roland
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Here's a link with more information. (I don't agree with all the info in this link, for instance the part about Magnus Effect drift left/low and right/high is flawed IMO but the G1 info seems sound)
Looks as though Roland's grasp of history is better than mine.
I still think the 750gr Hornady A-Max has a BC very nearly approximating 1 on the G1 scale. Close enough that it's often used as a reference or comparison bullet. And it's a modern boat tail projectile.
al
Looks as though Roland's grasp of history is better than mine.
I still think the 750gr Hornady A-Max has a BC very nearly approximating 1 on the G1 scale. Close enough that it's often used as a reference or comparison bullet. And it's a modern boat tail projectile.
al
Max, bullets have 2 -- or more -- ballistics coefficients depending how they perform at different speeds --or mach numbers, just to irritate Al. For example, how a bullet performs in the transonic region -- from the speed of sound to about 1400 fps -- can't be predicted with our current models. You can go to the Lyman pistol bullet book & find that some bullets "lose BC" and some gain at these speeds. All anyone can do is test, no one can predict.
So, most of us who shoot long range just try very hard to keep our bullets above the transonic region at the target. It might matter with a particular bullet, it might not. (& other bad things can happen in low end of the transonic region, as with the Sierra 168 grain International Match. Again, we're not sure why. And again, just avoid it.)
So to be practical with what you can do with BC: Back on your thread in the Long range forum, Alf found joy with the 190 grain Sierra in his .300 magnum. I suppose it is worth a try. A number of people, long ago, found joy with this bullet. Notice the "long ago." Two things: (1) because it was long ago, it is in a lot of books & "what some guy said" conversations. (2) We have a lot better bullet designs today.
As you probably know, most of us use BC to predict wind drift and bullet drop. To predict wind drift, all you really need is the wind velocity and the BC. It's arithmetic -- if you double the wind speed, you double the drift. Drop is another kettle of fish, you need time of flight. And it isn't arithmetic.
So, if you're shooting and don't know haw far away your target is, you better pay attention to drop. At long range, it's a much bigger variable than drift, unless you're shooting a hurricane. (As in the IBS Nationals in 1999. No fooling.)
But if you know the distance, and have a sight setting for it, you can forget drop and only worry about wind drift. So, to be practical, take a bullet like the 300 grain Berger .338. You can shoot that at 2800 fps and have a wind drift of 44 inches at 1,000 yards. Most pretty good .30 bullets will have a drift of over 64 inches at the same distance. Which bullet lets you make a wind-reading mistake & maybe get away with it? On the other hand, while that .338 Berger bullet only looses 900 fps over 1,000 yards, it takes it a good long time to get there. So if the distance were 1020 yards & you didn't know it, the high-speed .30 would help.
Back to the 190. You'd pick it only if (1) it was superbly accurate in your rifle, & you'll take your chances with the wind & range, or (2) it's the longest bullet that will stabilize with the twist you're using.
Now as to Al's remark. You can do most of your predicting from experience, skipping the math and modeling the ballisticians have to use for precision. But it's not fair to trash them. Their job is to use the best model they can determine to predict *exactly* what will happen. Again I can think of two reasons; there probably are more.
The first is to prevent some guy from going on an internet forum & complaining *he* got different results, and their model doesn't explain actual, empirical evidence. Or substitute "procurement officer" for "some guy," and "military testing" for "internet."
The second is to push the envelope with bullet design. If you have good predictive models, you can move farther, faster (usually) than if you just go by past experience, predicting with your gut.
& by the way Al, that's why ES and SD are different. SD is for prediction.
Consider this: Suppose there is a guy in Washington sate, named Al^2. Suppose further he looks just like Don Knotts. OK, generalizing, you could then say he looks like a movie star. Now in the common mind, "looking like a movie star" means you attract the hot chicks. See the problem?
So, most of us who shoot long range just try very hard to keep our bullets above the transonic region at the target. It might matter with a particular bullet, it might not. (& other bad things can happen in low end of the transonic region, as with the Sierra 168 grain International Match. Again, we're not sure why. And again, just avoid it.)
So to be practical with what you can do with BC: Back on your thread in the Long range forum, Alf found joy with the 190 grain Sierra in his .300 magnum. I suppose it is worth a try. A number of people, long ago, found joy with this bullet. Notice the "long ago." Two things: (1) because it was long ago, it is in a lot of books & "what some guy said" conversations. (2) We have a lot better bullet designs today.
As you probably know, most of us use BC to predict wind drift and bullet drop. To predict wind drift, all you really need is the wind velocity and the BC. It's arithmetic -- if you double the wind speed, you double the drift. Drop is another kettle of fish, you need time of flight. And it isn't arithmetic.
So, if you're shooting and don't know haw far away your target is, you better pay attention to drop. At long range, it's a much bigger variable than drift, unless you're shooting a hurricane. (As in the IBS Nationals in 1999. No fooling.)
But if you know the distance, and have a sight setting for it, you can forget drop and only worry about wind drift. So, to be practical, take a bullet like the 300 grain Berger .338. You can shoot that at 2800 fps and have a wind drift of 44 inches at 1,000 yards. Most pretty good .30 bullets will have a drift of over 64 inches at the same distance. Which bullet lets you make a wind-reading mistake & maybe get away with it? On the other hand, while that .338 Berger bullet only looses 900 fps over 1,000 yards, it takes it a good long time to get there. So if the distance were 1020 yards & you didn't know it, the high-speed .30 would help.
Back to the 190. You'd pick it only if (1) it was superbly accurate in your rifle, & you'll take your chances with the wind & range, or (2) it's the longest bullet that will stabilize with the twist you're using.
Now as to Al's remark. You can do most of your predicting from experience, skipping the math and modeling the ballisticians have to use for precision. But it's not fair to trash them. Their job is to use the best model they can determine to predict *exactly* what will happen. Again I can think of two reasons; there probably are more.
The first is to prevent some guy from going on an internet forum & complaining *he* got different results, and their model doesn't explain actual, empirical evidence. Or substitute "procurement officer" for "some guy," and "military testing" for "internet."
The second is to push the envelope with bullet design. If you have good predictive models, you can move farther, faster (usually) than if you just go by past experience, predicting with your gut.
& by the way Al, that's why ES and SD are different. SD is for prediction.
Consider this: Suppose there is a guy in Washington sate, named Al^2. Suppose further he looks just like Don Knotts. OK, generalizing, you could then say he looks like a movie star. Now in the common mind, "looking like a movie star" means you attract the hot chicks. See the problem?
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See what I mean?
LOL
BTW, I've used a cheesy Sierra program for at least 15yrs (it's on a floppy disc) for getting on target out to 1400yds.
It uses G1
I've used every bullet imaginable including plenty VLD's
We've never observed a problem, it's spot on, WELL within the parameters of any equipment to test.
As far as "the guy on the innernet" and his goofy complaints...... how you ever gonna' guard against human idiocy? Like his gun is accurate anyways???
and 'predictions?'
really
al
LOL
BTW, I've used a cheesy Sierra program for at least 15yrs (it's on a floppy disc) for getting on target out to 1400yds.
It uses G1
I've used every bullet imaginable including plenty VLD's
We've never observed a problem, it's spot on, WELL within the parameters of any equipment to test.
As far as "the guy on the innernet" and his goofy complaints...... how you ever gonna' guard against human idiocy? Like his gun is accurate anyways???
and 'predictions?'
really
al
In a lot of ways, I agree with you Al. But since I seem to like things in two's today, I got two reasons. The first is, he asked. The second is, if you just say fugidaboudit, people don't believe you.
A few of us use to shoot the 30-caliber 187 flatbase at 1K, and win a lot. So we'd preach about it on the long-range forum. Lots of snide remarks. Then Joel decided, "why give away an advantage?" I should delete my post.
A few of us use to shoot the 30-caliber 187 flatbase at 1K, and win a lot. So we'd preach about it on the long-range forum. Lots of snide remarks. Then Joel decided, "why give away an advantage?" I should delete my post.
M
max.burgess
Guest
Thanks Everyone
That is the first time I've seen the g7. I've loaded lots of 22cal. Ballistic Tips & they have a bc of about 250 so when I got the 95gr vld's I was surprised to see a bc of 250 on the box.
Thanks Max
That is the first time I've seen the g7. I've loaded lots of 22cal. Ballistic Tips & they have a bc of about 250 so when I got the 95gr vld's I was surprised to see a bc of 250 on the box.
Thanks Max
J
J. Valentine
Guest
G1 and G7 are drag functions that suit a particular shape bullet. As most bullet makers like to show a big number BC they usually quote a G1 BC that results in the bigger number. However the G1 function may not actually suit the bullet very well and at some point in it's trajectory the G1 BC results in less ballistic calculation accuracy. Berger know this and by listing both the G1 and the G7 the smaller number of the G7 BC is not a big shock to the customer as they are more used to the bigger G1 number.
If the bullets shape is a match for the G7 drag function then the smaller BC number will result in a more accurate trajectory prediction . Berger have put the G7 BC on there because they know it is the more accurate BC for that bullet.
It is true that one single BC can not describe or predict a whole trajectory as well as multipe BC's taken at multiple velocity boundries. However the multiple BC's need to be of the one same drag function . You could not use a G1 and a G7 BC in the same trajectory calculation.
If the bullets shape is a match for the G7 drag function then the smaller BC number will result in a more accurate trajectory prediction . Berger have put the G7 BC on there because they know it is the more accurate BC for that bullet.
It is true that one single BC can not describe or predict a whole trajectory as well as multipe BC's taken at multiple velocity boundries. However the multiple BC's need to be of the one same drag function . You could not use a G1 and a G7 BC in the same trajectory calculation.
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M
mks
Guest
Exactly. As I understand it, Bryan Litz pushed Berger to include the G7 BC. Here is his explanation:
http://www.longrangehunting.com/articles/berger-g7-ballistic-coefficient-1.php
Cheers,
Keith