Is the ballistic coefficient a measure of drag on the bullet? In the 7mm rem mag accubonds of 160 grain have a coefficient of 531 which is the highest of all the bullet sizes. Does this mean that, all other things equal, that bullets of that grain will be the most accurate for accubonds?
Ballistic coefficient
- Thread starter mackillan
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No, it doesn't mean that it will be the most accurate, it means that it will slow down slower. This can have a large effect on drop and wind drift at long ranges, and perhaps nothing to get excited about at traditional hunting ranges.
My new-to-me .338 Edge shoots at 300 grain bullet with a BC of .768 or so, for the express purpose of trying to beat the wind.
Frozen Snake
Regular
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The BC has to do with how easily the bullet will slip through the air. The lower BC bullets will shed speed more quickly because of the increased air resistance. This slowing down of course affects trajectory and downrange energy.It has nothing to do with accuracy. just drop, wind drift etc.
Lets say two bullets are of the same caliber and weight, the one with the higher BC will have less drop, wind drift, and more retained energy. this becomes more recognizable the farther the bullet travels from the muzzle. It is a calculation of bullet length, mass, cross sectional area, density, and drag coefficient.
All of this does not make a difference when shots are out to 300 yards or less.
Makes a huge difference for the Long Range guys that shoot out to 1000 yards.
Lets say two bullets are of the same caliber and weight, the one with the higher BC will have less drop, wind drift, and more retained energy. this becomes more recognizable the farther the bullet travels from the muzzle. It is a calculation of bullet length, mass, cross sectional area, density, and drag coefficient.
All of this does not make a difference when shots are out to 300 yards or less.
Makes a huge difference for the Long Range guys that shoot out to 1000 yards.
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So, it not not an indication of consistency but is flatter shooting? In the field, unless one is able to measure distance perfectly, wouldnt this usually result in an increase in accuracy?
Mackillan, the highest of all bullets size for the 7mm/.284 is not 531 take a look at Berger VLDs 180gr, they have a BC of 684 much higher than the accubonds.Watched a video on Wild TV last week fellow shot a Elk at over 700 yards with the 168gr VLD berger and another at over 600y with 180gr vld on large grizzle bear. Supposedly out of buisness now Lost River Bullets made some at well over 700 BC
If you were taking shots in at 300+m, but at unknown distance, yes the flatter shooting bullets would impact closer to the point of aim, all things being equal.
However, it's possible that the groups size of the low-drag bullets may be larger than the difference in the drop. It's also possible that the low drag bullet will not perform on the game as well as the less slippery bullet.
At 300+ you generally have a bit more time to estimate your range.
For instance, with a 200 yard zero, that Accubond at 3000 FPS drops 6.4" at 300 yards, 18.5" at 400 and 37.2" at 500, whereas the 160 grain Partition drops 6.6", 19.2" and 38.7" at the same distances. So by the time you've got to 500 yards, you only drop about 1.5" more. What are the chances of you shooting a 3" group at 500 yds? (a circle with the 1.5" radius)
Heck, even the 175 grain Partition, a not terribly slick bullet, at 2900 FPS will drop 7.0", 20.2" and 40.4", so even giving-up 100 FPS, it only drops 3.2" more than the Accubond at 500 yards.
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Accuracy is in the barrel, and action / bolt fitting.
The bullet with a high BC, will get to the target with less drift/drop than one with a smaller number(same weight). So its safe to say yes high BC is a good thing for long range shooting. In 7 mil I liked the 168 Sierra Match
The bullet with a high BC, will get to the target with less drift/drop than one with a smaller number(same weight). So its safe to say yes high BC is a good thing for long range shooting. In 7 mil I liked the 168 Sierra Match
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- Somewhere on the Hudson Bay Coast
Something to consider is that BC as a measure of bullet performance through the air is really only useful for the bullets from a particular manufacturer. The reason for this is that not all bullets are made in the same place and differences in air density effect the performance of the bullet, so the same bullet might be allocated a different BC in different parts of the country. When Sierra moved their operation, some of their published BC's changed significantly.
Because the BC is essentially a sectional density calculation with a form factor added to the mix, it creates another variable between manufacturers. The form factor used by company A will not be identical to that used by company B, so again when the BC's are not dissimilar, the differences are only useful if both BC's are published by the same company.
The final fly in the ointment is that bullet manufacturers fudge the numbers, because advertised BC's are a marketing tool. So what is the poor shooter to do? Pick the bullet whose construction most closely matches your needs, and shoot it over a variety of ranges, particularly if you are a long range shooter, noting the drop at particular ranges. Thus you can make a drop table pertinent to your rifle and load, one that is superior to computer generated drop tables. From your drop table you can determine how closely your bullet matches the published BC.
Because the BC is essentially a sectional density calculation with a form factor added to the mix, it creates another variable between manufacturers. The form factor used by company A will not be identical to that used by company B, so again when the BC's are not dissimilar, the differences are only useful if both BC's are published by the same company.
The final fly in the ointment is that bullet manufacturers fudge the numbers, because advertised BC's are a marketing tool. So what is the poor shooter to do? Pick the bullet whose construction most closely matches your needs, and shoot it over a variety of ranges, particularly if you are a long range shooter, noting the drop at particular ranges. Thus you can make a drop table pertinent to your rifle and load, one that is superior to computer generated drop tables. From your drop table you can determine how closely your bullet matches the published BC.
Mystic Precision
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Bullet makers are now aware of the negative press they can get with overly optimistic BC ratings.
Both Sierra and Berger test their bullets in real world settings. Not sure if anyone else does. That is as close as you will get given the differences in barrels and environment.
For the most part, the BC rating and a muzzle velocity will let you generate a drop chart that will be close - get you on paper. With the differences due to barrel, optics/rangefinders and shooters, it is always best to confirm your drop chart based on your shooting.
Like most LR shooters, I strive for the highest BC bullets launched at their optimum velocity (not necessarily the fastest) for best LR ballistics. That reduction in wind drift helps me be more accurate.
As for LR hunting needs, a really important factor to keep in mind is impact velocity. All bullets are going to slow down way out there. A 'fragile' bullet at close range, may just be the perfect bullet at LR.
Jerry
Both Sierra and Berger test their bullets in real world settings. Not sure if anyone else does. That is as close as you will get given the differences in barrels and environment.
For the most part, the BC rating and a muzzle velocity will let you generate a drop chart that will be close - get you on paper. With the differences due to barrel, optics/rangefinders and shooters, it is always best to confirm your drop chart based on your shooting.
Like most LR shooters, I strive for the highest BC bullets launched at their optimum velocity (not necessarily the fastest) for best LR ballistics. That reduction in wind drift helps me be more accurate.
As for LR hunting needs, a really important factor to keep in mind is impact velocity. All bullets are going to slow down way out there. A 'fragile' bullet at close range, may just be the perfect bullet at LR.
Jerry
Sorry I meant of the accubonds. Now I will have to buy a new manual for the Berger
I have only started researching loading after buying all the equipment. I am starting on the accubonds(have purchased 1000 120, 140,160 and some partitions) and also 45/70 government for Shiloh Sharps. 180 grains is quite the size. Would the velocity be highest for these?
I have only started researching loading after buying all the equipment. I am starting on the accubonds(have purchased 1000 120, 140,160 and some partitions) and also 45/70 government for Shiloh Sharps. 180 grains is quite the size. Would the velocity be highest for these?
Sorry I meant of the accubonds. Now I will have to buy a new manual for the Berger I have only started researching loading after buying all the equipment. I am starting on the accubonds(have purchased 1000 120, 140,160 and some partitions) and also 45/70 government for Shiloh Sharps. 180 grains is quite the size. Would the velocity be highest for these? Is the cree word manitou known in other native languages?
I have only started researching loading after buying all the equipment. I am starting on the accubonds(have purchased 1000 120, 140,160 and some partitions) and also 45/70 government for Shiloh Sharps. 180 grains is quite the size. Would the velocity be highest for these? Is the cree word manitou known in other native languages?
