Wind, bullets and trajectory.
08-03-2003, 02:13 PM
#11
Giant Nontypical
Join Date: Feb 2003
Location: fort mcmurray alberta canada
Posts: 5,667
RE: Wind, bullets and trajectory.
The original question of this thread was whether or not smaller lighter bullets would be affected by wind more than larger heavier ones.Several people immediately agreed that weight and momentum was the deciding factor.After I proved this to be incorrect some people chose to start adding conditions and what if' s and all other things being equal etc.The point is that sheer weight does not decide wind drift.It is true that heavier bullets could be affected less by wind but it is also true that lighter bullets could be less affected by wind but the deciding factor is the shape of the bullet and not it' s weight.
08-03-2003, 03:45 PM
#12
Nontypical Buck
Join Date: Feb 2003
Location: Michigan
Posts: 3,476
RE: Wind, bullets and trajectory.
I couldn' t agree more.
If I had to choose a bullet to buck the wind, I would just pick the shape that was the " slickest" and stuff it into my most accurate firearm.
Seems to me I once went on a " quest" for the slickest of the slick. If I remember correctly it seemes that the .284 match bullets were among the best.
BTW, In my first example of the running backs, they were wearing the same shaped helmet ;-)
If I had to choose a bullet to buck the wind, I would just pick the shape that was the " slickest" and stuff it into my most accurate firearm.
Seems to me I once went on a " quest" for the slickest of the slick. If I remember correctly it seemes that the .284 match bullets were among the best.
BTW, In my first example of the running backs, they were wearing the same shaped helmet ;-)
08-03-2003, 06:58 PM
#13
Giant Nontypical
Thread Starter
Join Date: Feb 2003
Location: Missouri USA
Posts: 5,420
RE: Wind, bullets and trajectory.
It just seems to me that if something is suspended in air as a bullet is between the muzzle and its target as long as they are the same size and if it takes exactly the same amount of time to reach the target they should be affected the very same.
If you had 2 round balls the same size but 1 weighed 100lbs and the other weighed 10lb and dropped them off a 10 story building at the same time which one would hit the ground first?
If you had 2 round balls the same size but 1 weighed 100lbs and the other weighed 10lb and dropped them off a 10 story building at the same time which one would hit the ground first?
08-03-2003, 07:42 PM
#14
Giant Nontypical
Join Date: Feb 2003
Location: fort mcmurray alberta canada
Posts: 5,667
RE: Wind, bullets and trajectory.
Strut-First of all, all bullets will not strike the target in the same amount of time.Even if two bullets of the same weight are fired at exactly the same velocity but are shaped different the one with the highest ballistic co-efficient will reach the target first and drop the least.
08-03-2003, 08:11 PM
#15
Giant Nontypical
Thread Starter
Join Date: Feb 2003
Location: Missouri USA
Posts: 5,420
RE: Wind, bullets and trajectory.
I know stubblejumper, that was a hypothetical situtation, but almost everyone has the theory of a light weight bullet being affected more than a heavier one and thats wrong, I was just stating that if a person could get the exact same shape and the exact same time to reach the target it should be affected the same. Matter of fact a 55 grain 22-250 traveling at 3400 fps would be affected less than a 170 grain 30-30 shooting both in a 30 MPH cross wind. From the time the bullet leaves the muzzle until it hits the target it should be blown off the same amount the wind has moved in the same exact time, in other words if it takes a bullet 1/10th of a second to hit the target then however far the 30 mph crosswind has moved in that 1/10th of a second is how far your bullet will be moved.
Just like bullet drop, if you could drop a bullet at the same exact time that one leaves your muzzle then the drop will be the same, if it takes your bullet 1/10th of a second to hit the target then however far the bullet you dropped fell in that 1/10th of a second should be the same as the bullet your shooting.
Just like bullet drop, if you could drop a bullet at the same exact time that one leaves your muzzle then the drop will be the same, if it takes your bullet 1/10th of a second to hit the target then however far the bullet you dropped fell in that 1/10th of a second should be the same as the bullet your shooting.
08-03-2003, 11:00 PM
#16
Nontypical Buck
Join Date: Feb 2003
Location: Body in SE WI, mind in U.P.
Posts: 4,781
RE: Wind, bullets and trajectory.
Everything depends on two things- Ballistic coefficient and velocity, with BC being much more important.
BC is the aerodynamic property of a bullet. Its actually based on how a bullet fairs in comparison with the ' ideal bullet' also known as a ' Krupps bullet' which is a very aeordynamic object.
When a bullet is fired, the friction caused by air has a much greater effect on the trajectory than gravity itself. one way to minimize the effect of air- whether it be air the bullet is displacing in flight or crosswinds is to have an aerodynamic design.
Here' s a good example:
If on a very windy day you were to take a football and a soccer ball that weighed the same and throw them both through the air at 30 mph at a 45 degree angle- which do you think would go farther and be less effected by the wind (lets say you throw a perfect spiral on the football to similate the rifling action on a bullet and also put equal spin on the soccer ball). The footballwould of course go farther and be less moved by the wind.
The exact same thing goes for bullet projectiles. A .30 180 gr round nosed bullet fired alongside a .30 180 spitzer bullet would hit the ground at the same time, but the spitzer bullet would go much farther in the same amount of time. In fact the round nosed bullet would lose velocity very quickly after 200 yards and its trajectory would litterally drop off in relation to the spitzer bullet.
I also mentioned velocity. velocity will give you an added advantage to bucking the wind if the BC is equal. A 168gr match bullet with a BC of .450 fired from a .308 and from a .300 magnum will show different trajectories- the faster bullet from the .300 magnum will obviously drop less and will have less wind drift than the .308 at any particular range because it reaches the target sooner and is exposed to wind for a shorter period of time.
If you were to take the same 168 gr match bullet and fire it from a .308 at about 2700 fps and were able to take a 110 gr .30 caliber bullet with a BC of .240 but get 3000 fps out of the .308 and were to fire them side by side, you would get a whole differetn effect.You would get roughly half as much drift with the match bullet, which gets very significant with more wind and distance, the trajectory will favor the lighter bullet to about 300 yards where the heavier more aerodynamic bullet will start to retain alot mor eenergy and will begin to drop less.
Another case I would like to make for the importance of BC has to do with the .50 BMG round. I had the opportunity to shoot a homebuilt .50 rifle a few months ago which was a heck of alot of fun[8D] The big suprise came when I asked the guy what kind of velocity he was getting with the 700 gr bullets, I was expecting 3000-4000 fps judging by the size of the cartridge, the recoil, and the noise it made, not to mention it reputation as a sniper round used to distances up to a mile. He told me 2600 fps! I did some research on the cartridge later and found out that indeed, they are loaded to shoot around 2600 fps, but the bullet has an incredible BC of around 1.05. The secret of the .50 BMG is not velocity but the aerodynamics of the bullet to hit targets at incredibly lomng ranges.
BC is the aerodynamic property of a bullet. Its actually based on how a bullet fairs in comparison with the ' ideal bullet' also known as a ' Krupps bullet' which is a very aeordynamic object.
When a bullet is fired, the friction caused by air has a much greater effect on the trajectory than gravity itself. one way to minimize the effect of air- whether it be air the bullet is displacing in flight or crosswinds is to have an aerodynamic design.
Here' s a good example:
If on a very windy day you were to take a football and a soccer ball that weighed the same and throw them both through the air at 30 mph at a 45 degree angle- which do you think would go farther and be less effected by the wind (lets say you throw a perfect spiral on the football to similate the rifling action on a bullet and also put equal spin on the soccer ball). The footballwould of course go farther and be less moved by the wind.
The exact same thing goes for bullet projectiles. A .30 180 gr round nosed bullet fired alongside a .30 180 spitzer bullet would hit the ground at the same time, but the spitzer bullet would go much farther in the same amount of time. In fact the round nosed bullet would lose velocity very quickly after 200 yards and its trajectory would litterally drop off in relation to the spitzer bullet.
I also mentioned velocity. velocity will give you an added advantage to bucking the wind if the BC is equal. A 168gr match bullet with a BC of .450 fired from a .308 and from a .300 magnum will show different trajectories- the faster bullet from the .300 magnum will obviously drop less and will have less wind drift than the .308 at any particular range because it reaches the target sooner and is exposed to wind for a shorter period of time.
If you were to take the same 168 gr match bullet and fire it from a .308 at about 2700 fps and were able to take a 110 gr .30 caliber bullet with a BC of .240 but get 3000 fps out of the .308 and were to fire them side by side, you would get a whole differetn effect.You would get roughly half as much drift with the match bullet, which gets very significant with more wind and distance, the trajectory will favor the lighter bullet to about 300 yards where the heavier more aerodynamic bullet will start to retain alot mor eenergy and will begin to drop less.
Another case I would like to make for the importance of BC has to do with the .50 BMG round. I had the opportunity to shoot a homebuilt .50 rifle a few months ago which was a heck of alot of fun[8D] The big suprise came when I asked the guy what kind of velocity he was getting with the 700 gr bullets, I was expecting 3000-4000 fps judging by the size of the cartridge, the recoil, and the noise it made, not to mention it reputation as a sniper round used to distances up to a mile. He told me 2600 fps! I did some research on the cartridge later and found out that indeed, they are loaded to shoot around 2600 fps, but the bullet has an incredible BC of around 1.05. The secret of the .50 BMG is not velocity but the aerodynamics of the bullet to hit targets at incredibly lomng ranges.
08-03-2003, 11:10 PM
#17
Nontypical Buck
Join Date: Feb 2003
Location: Body in SE WI, mind in U.P.
Posts: 4,781
RE: Wind, bullets and trajectory.
Another thing there is extensive literature written on has to do with bullets used in AR-15 rifles. When used for target shooting, 69 gr. match bullets shoot very accurately out to 300 yards. After this point, if the shooter does not change buulets, .30 rifles, even the old M1 Garands will out shoot the AR-15' s. On the 600 yard targets, an AR shooter needs to switch to 80 gr bullets (usually 69 gr or lighter bullets would be used for shorter courses of fire) if they don' t want their bullets blown all over the target. Here they are sacrificing velocity for aerodynamis and gain huge dividends in being able to mitigate the wind effects.
08-04-2003, 01:24 AM
#18
Nontypical Buck
Join Date: Feb 2003
Location: Michigan
Posts: 3,476
RE: Wind, bullets and trajectory.
Briman,
This explanation you have offered then bears evidence that a HEAVIER bullet can out perform a lighter bullet (assuming similar shape here) where wind bucking is concerned. And if this is so, it is mainly b/c of the superior BC of the heavier bullet.......i.e. the 50 BMG. ?????
This explanation you have offered then bears evidence that a HEAVIER bullet can out perform a lighter bullet (assuming similar shape here) where wind bucking is concerned. And if this is so, it is mainly b/c of the superior BC of the heavier bullet.......i.e. the 50 BMG. ?????
08-04-2003, 05:49 AM
#19
Giant Nontypical
Join Date: Feb 2003
Location: Texas - BUT NOW in Madison County, NY
Posts: 6,270
RE: Wind, bullets and trajectory.
Briman is correct - the B.C. number of a bullet shows how much it will be affected by wind (actually, how efficiently it resists deceleration in air due to drag).
B.C. is determined by two factors: the SECTIONAL DENSITY of the bullet (weight in pounds divided by the square of the diameter); and the form factor, or shape of the bullet. Thus, a quite heavy blunt or round-nosed bullet can have a B.C. that is lower than a lighter, sharper bullet. In such a case, if fired at the same initial velocity, the heavy, blunt (lower B.C.) bullet will be affected MORE by wind than the lighter one. Big old round-nose .45/70 bullets drift like hell!! However, if you sharpen up the heavier one to the point that it' s ballistic coefficient exceeds that of the lighter bullet, the heavier one will then perform better.
So there are two things that determine how well a given projectile will perform in the wind: weight AND shape. If you compare the ballistic coefficents of two different bullets, the one with the higher B.C. number will be less affected by wind than the other, regardless of which one weighs the most!! This is assuming they both are launched with the same initial velocity.
Bullets with higher B.C. also drop less while travelling any given distance, because they are better at retaining initial velocity, and thus cover that particular distance in less time, giving gravity less time to act upon them over that distance.
B.C. is determined by two factors: the SECTIONAL DENSITY of the bullet (weight in pounds divided by the square of the diameter); and the form factor, or shape of the bullet. Thus, a quite heavy blunt or round-nosed bullet can have a B.C. that is lower than a lighter, sharper bullet. In such a case, if fired at the same initial velocity, the heavy, blunt (lower B.C.) bullet will be affected MORE by wind than the lighter one. Big old round-nose .45/70 bullets drift like hell!! However, if you sharpen up the heavier one to the point that it' s ballistic coefficient exceeds that of the lighter bullet, the heavier one will then perform better.
So there are two things that determine how well a given projectile will perform in the wind: weight AND shape. If you compare the ballistic coefficents of two different bullets, the one with the higher B.C. number will be less affected by wind than the other, regardless of which one weighs the most!! This is assuming they both are launched with the same initial velocity.
Bullets with higher B.C. also drop less while travelling any given distance, because they are better at retaining initial velocity, and thus cover that particular distance in less time, giving gravity less time to act upon them over that distance.
08-04-2003, 06:16 AM
#20
Giant Nontypical
Thread Starter
Join Date: Feb 2003
Location: Missouri USA
Posts: 5,420
RE: Wind, bullets and trajectory.
In other words then just because a bullet is heavy don' t mean that it will out perform a lighter one then in the wind, Thats my point. Most people think that a light bullet will be blown off alot more than a heavy one which is wrong, there is alot more to it than just the weight of the bullet.