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Range Report Spindrift Calculation??
- Thread starter ChadTRG42
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Re: Spindrift Calculation??
Bryan Lutz,
Unlike a few in this thread I am here to learn. I also believe in, no pain no gain, my question is this.
Given Std Day data, at 800asl, a 175 SMK leaving a 11.27 R/H twist barrel at 2725-2750fps what is the SD to 1K assuming barrel an target are at the same horz. start and stop point? Then add a 3mph wind from both 3 an 9 if you would be so kind?
Also a 190SMK leaving a 10 twist at 3125-3150fps everything else the same?
Could be trigger, wind, whatever, or whoever but I have my retical canted 1moa to the left at 1k for the 175smk and 5/8 moa for the 190smk, which seems to work for me.
I would like to know your answer on this question, as well as from anyone else that can shed light, without jumping track.
Should you not want to display the answer but, do run the numbers, please PM or E-mail me.
Thanks,
Kenneth
Bryan Lutz,
Unlike a few in this thread I am here to learn. I also believe in, no pain no gain, my question is this.
Given Std Day data, at 800asl, a 175 SMK leaving a 11.27 R/H twist barrel at 2725-2750fps what is the SD to 1K assuming barrel an target are at the same horz. start and stop point? Then add a 3mph wind from both 3 an 9 if you would be so kind?
Also a 190SMK leaving a 10 twist at 3125-3150fps everything else the same?
Could be trigger, wind, whatever, or whoever but I have my retical canted 1moa to the left at 1k for the 175smk and 5/8 moa for the 190smk, which seems to work for me.
I would like to know your answer on this question, as well as from anyone else that can shed light, without jumping track.
Should you not want to display the answer but, do run the numbers, please PM or E-mail me.
Thanks,
Kenneth
G
Guest
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Re: Spindrift Calculation??
Yep, and it's not over yet.
Seems, some folks take sig lines as a joke.
I'm going to ask at Serria first if nj, all the answers are within the confines of Redstone in Huntsville Alabama, if I have to go that route. Time frame for same, unknown, but I do know folks, that know folks, that can solve the issue at hand.
I know those two words (NASA-ALABAMA)seem odd togeather but we hillbillys can Git-R-Dun.
Those that are here or pass threw, that could answer, might be out of bandaids, compress, or tourniquet's and I fully understand that but,.... like Jesse said, I don't have time to bleed.
Yep, and it's not over yet.
Seems, some folks take sig lines as a joke.
I'm going to ask at Serria first if nj, all the answers are within the confines of Redstone in Huntsville Alabama, if I have to go that route. Time frame for same, unknown, but I do know folks, that know folks, that can solve the issue at hand.
I know those two words (NASA-ALABAMA)seem odd togeather but we hillbillys can Git-R-Dun.
Those that are here or pass threw, that could answer, might be out of bandaids, compress, or tourniquet's and I fully understand that but,.... like Jesse said, I don't have time to bleed.
Re: Spindrift Calculation??
Gunfighter14e2,
I understand and admire your quest to figure out someway on compensating for spin drift but I truly believe you’re wasting a lot of time and effort on this for nothing. I enjoy math and a challenge for the most part, but there are times when there are too many variables to calculate and I firmly believe spin drift is one of them. As I’ve stated in a controlled windless environment calculation could be made for spin drift. In the real world of shooting there are just too many variables.
You’ll rarely find a constant 3 mph wind blowing from x to y across the entire bullet path. Earlier this summer we were shooting ground hogs down in the mountains of Highland County Va. At times we were shooting over a grand between the two mountain ridges. We figured the winds at one point to be 8 to 10 mph blowing from 9 to 3 wind starting around 75 yards and to about 300 yards. We were watching the tress, hay and bushes blowing in the wind. At about 500 yards we picked up a 10 to 15 mph cross wind blowing from 2 to 8 o’clock but couldn’t tell where or when it stopped. Around 800 yards we had a 5 mph wind blowing from 4 to 10 o’clock. What we couldn’t see was the wind blowing 100 to 300 feet above the ground where the bullets path was going to take across between the two ridges.
These are the real world environments I shoot in when I go back east to ground hog hunt or I go out west to PD hunt. Even if I knew the exact spin drift for this shot, let’s just say 1 moa right would be my spin drift, what good would it do me? I still have multiple cross winds to deal with and they’re a much bigger factor than worrying about spin drift. Any spin drift will be factored into my overall windage correction.
My best advice, if you learn to dope the wind well, you’ll consciously or sub-consciously take care of any spin drift corrections. Even if you find a calculation for SD, the first inconsistent wind across the bullet flight path or cross wind will cancel out any corrections for SD.
Hope that helps.
Gunfighter14e2,
I understand and admire your quest to figure out someway on compensating for spin drift but I truly believe you’re wasting a lot of time and effort on this for nothing. I enjoy math and a challenge for the most part, but there are times when there are too many variables to calculate and I firmly believe spin drift is one of them. As I’ve stated in a controlled windless environment calculation could be made for spin drift. In the real world of shooting there are just too many variables.
You’ll rarely find a constant 3 mph wind blowing from x to y across the entire bullet path. Earlier this summer we were shooting ground hogs down in the mountains of Highland County Va. At times we were shooting over a grand between the two mountain ridges. We figured the winds at one point to be 8 to 10 mph blowing from 9 to 3 wind starting around 75 yards and to about 300 yards. We were watching the tress, hay and bushes blowing in the wind. At about 500 yards we picked up a 10 to 15 mph cross wind blowing from 2 to 8 o’clock but couldn’t tell where or when it stopped. Around 800 yards we had a 5 mph wind blowing from 4 to 10 o’clock. What we couldn’t see was the wind blowing 100 to 300 feet above the ground where the bullets path was going to take across between the two ridges.
These are the real world environments I shoot in when I go back east to ground hog hunt or I go out west to PD hunt. Even if I knew the exact spin drift for this shot, let’s just say 1 moa right would be my spin drift, what good would it do me? I still have multiple cross winds to deal with and they’re a much bigger factor than worrying about spin drift. Any spin drift will be factored into my overall windage correction.
My best advice, if you learn to dope the wind well, you’ll consciously or sub-consciously take care of any spin drift corrections. Even if you find a calculation for SD, the first inconsistent wind across the bullet flight path or cross wind will cancel out any corrections for SD.
Hope that helps.
Re: Spindrift Calculation??
Jeff,
If you have MOA drift, NO matter what the wind is doing....
Then it seems to me, the correction should be dialed in, dependant on the twist(Left/Right).
Then make corections for CURRENT winds.............
Where am I off?.
Since we are dealing with an absolute.........would we not factor it into the mix.
I know a damn fine shooter, who dials a MOA in at 1k, before he even starts...........
A lot of folks know him here, and he is a borderline math genius.
Jeff,
If you have MOA drift, NO matter what the wind is doing....
Then it seems to me, the correction should be dialed in, dependant on the twist(Left/Right).
Then make corections for CURRENT winds.............
Where am I off?.
Since we are dealing with an absolute.........would we not factor it into the mix.
I know a damn fine shooter, who dials a MOA in at 1k, before he even starts...........
A lot of folks know him here, and he is a borderline math genius.
Re: Spindrift Calculation??
Shoes, you are about 8 pages too late, and we already discussed the fact that, if you are 1 MOA short or long at 1000 yards, and you are engaging an 18" wide target, you missed the target regardless. Have your math genius run the numbers.
The bottom line is, no one can call the wind to the required accuracy, hence the difference is "lost" in the wind... otherwise wind charts are meaningless without a SD correction and would have to be read as such.
What happens is, we measure for 10 MPH, we dial, and across the course the wind changes, negating the difference.
I am going to run a blind statistical experiment where everyone can email an image of their target at 100 yards, and well see what percentage of the impacts favor right and by how much to correlate the amount of drift associated to bad shots or varying zeros.
Shoes, you are about 8 pages too late, and we already discussed the fact that, if you are 1 MOA short or long at 1000 yards, and you are engaging an 18" wide target, you missed the target regardless. Have your math genius run the numbers.
The bottom line is, no one can call the wind to the required accuracy, hence the difference is "lost" in the wind... otherwise wind charts are meaningless without a SD correction and would have to be read as such.
What happens is, we measure for 10 MPH, we dial, and across the course the wind changes, negating the difference.
I am going to run a blind statistical experiment where everyone can email an image of their target at 100 yards, and well see what percentage of the impacts favor right and by how much to correlate the amount of drift associated to bad shots or varying zeros.
Re: Spindrift Calculation??
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">The bottom line is, no one can call the wind to the required accuracy, hence the difference is "lost" in the wind... otherwise wind charts are meaningless without a SD correction and would have to be read as such.
What happens is, we measure for 10 MPH, we dial, and across the course the wind changes, negating the difference. </div></div>
Frank,
Well said, hence the difference is "lost" in the wind. Exactly what I've been trying to say, I like it!
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">The bottom line is, no one can call the wind to the required accuracy, hence the difference is "lost" in the wind... otherwise wind charts are meaningless without a SD correction and would have to be read as such.
What happens is, we measure for 10 MPH, we dial, and across the course the wind changes, negating the difference. </div></div>
Frank,
Well said, hence the difference is "lost" in the wind. Exactly what I've been trying to say, I like it!
Re: Spindrift Calculation??
Frank,
Ok, I see how your negating, and agree..........
At 100yds, (if I read you correctly), there will no DRIFT...........
Any direction regardless of twist, unless there's a stout breeze........
So, what's the purpose of that test/.
Just asking, I haven't a clue.........
Frank,
Ok, I see how your negating, and agree..........
At 100yds, (if I read you correctly), there will no DRIFT...........
Any direction regardless of twist, unless there's a stout breeze........
So, what's the purpose of that test/.
Just asking, I haven't a clue.........
Re: Spindrift Calculation??
It is simple... most test as noted above are done in the field and everyone can agree field testing is not accurate... especially trying to determine true SD as opposed to other factors.
Now, people can run numbers using a computer model, to extrapolate what the actual drift would be if shot in a vacuum, however we don't shoot in a vacuum, nor does it take into account shooter errors.
Now, just off the cuff, if you look at things like this thread here as well as others like it, you might see the same thing I see at the range every time we have a class or competition.
3 Shot group thread
What I see is round after round of shooter error. To demonstrate this, and what potential it has at 1000 yards or more, we look no further than 100 yards.
Now, I don't want to single anyone out, so a blind test, to statistcally show that most people favor right, as much as a 1 MOA, but closer to .5 MOA, which at 1000 yards, compounded with 1 MOA of SD should be devastiting to a field shooter.
Look,
Note the number of shots right of the target...
again,
more, this time at 200 yards
here, and you get the picture
Just peruse through the threads of people who post images of their 100 yard, 200 yards, groups, etc. Count how many shots are taken and how many go right and how far. This information cannot be ignored and must be accounted for downrange...
So, we have wind, spindrift, and shooter error, where does this put the shot.
Its fine if you feel dialing 1 MOA is necessary, however it is an arbitrary number by everyone's admission. It has been rounded, adjusted for, and most important calculated in the field by HUMAN shooters... who have problems whether they want to admit it or not. Lucky for most proponents, people use right hand twist barrels that are on rifles owned by right handed shooters, so adding a correction for right handed drift is a pretty safe bet in anyone's book.
It is simple... most test as noted above are done in the field and everyone can agree field testing is not accurate... especially trying to determine true SD as opposed to other factors.
Now, people can run numbers using a computer model, to extrapolate what the actual drift would be if shot in a vacuum, however we don't shoot in a vacuum, nor does it take into account shooter errors.
Now, just off the cuff, if you look at things like this thread here as well as others like it, you might see the same thing I see at the range every time we have a class or competition.
3 Shot group thread
What I see is round after round of shooter error. To demonstrate this, and what potential it has at 1000 yards or more, we look no further than 100 yards.
Now, I don't want to single anyone out, so a blind test, to statistcally show that most people favor right, as much as a 1 MOA, but closer to .5 MOA, which at 1000 yards, compounded with 1 MOA of SD should be devastiting to a field shooter.
Look,
Note the number of shots right of the target...
again,
more, this time at 200 yards
here, and you get the picture
Just peruse through the threads of people who post images of their 100 yard, 200 yards, groups, etc. Count how many shots are taken and how many go right and how far. This information cannot be ignored and must be accounted for downrange...
So, we have wind, spindrift, and shooter error, where does this put the shot.
Its fine if you feel dialing 1 MOA is necessary, however it is an arbitrary number by everyone's admission. It has been rounded, adjusted for, and most important calculated in the field by HUMAN shooters... who have problems whether they want to admit it or not. Lucky for most proponents, people use right hand twist barrels that are on rifles owned by right handed shooters, so adding a correction for right handed drift is a pretty safe bet in anyone's book.
G
Guest
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Re: Spindrift Calculation??
I don't think we are on the same page here. I am not looking for the S/D answer to comp anything. I am looking for the answer for a reason no one as brought up yet.
I don't think there are many fence riders on this one, hence the quest. This site has had more heart burn over this question than any other over the years. Two of the best Shooters on this rock left this site because of cat fights, just like this. They both tried to explain the issue at hand and were laughed at. Seems only numbers fly around here so I <span style="font-weight: bold">will </span> find at least 3 guys that can run the numbers via the JBM or guys that have papers on them, that have no interest in the outcome either way. The 3mph will explain it's self in the end.
Funny thing is, E-mails from some known (none papered) number crunchers are saying the 175 is correct within 10% but the 190 is off by 16%. Being these are <span style="font-weight: bold">NOT </span> papered crunchers I will wait for papered, so there is no mistake what so ever.
I don't think we are on the same page here. I am not looking for the S/D answer to comp anything. I am looking for the answer for a reason no one as brought up yet.
I don't think there are many fence riders on this one, hence the quest. This site has had more heart burn over this question than any other over the years. Two of the best Shooters on this rock left this site because of cat fights, just like this. They both tried to explain the issue at hand and were laughed at. Seems only numbers fly around here so I <span style="font-weight: bold">will </span> find at least 3 guys that can run the numbers via the JBM or guys that have papers on them, that have no interest in the outcome either way. The 3mph will explain it's self in the end.
Funny thing is, E-mails from some known (none papered) number crunchers are saying the 175 is correct within 10% but the 190 is off by 16%. Being these are <span style="font-weight: bold">NOT </span> papered crunchers I will wait for papered, so there is no mistake what so ever.
Re: Spindrift Calculation??
I'll say, if someone of note is scared off by this and I personally don't see it as a cat fight, then the information they are bringing to the table is weak at best and probably falls in the "it works for me" category.
Otherwise with success and solid foundation in their reasoning there is no fight ? or debate.
There are tons of things that "work for me" in field, how I carry a ruck and can move farther and faster than guys twice my size. Does that mean I can explain it to someone else... no. so my reasoning by itself falls flat.
Hiding behind anything tells volumes in my opinion as does being scared away from debate, as no one is getting ugly, people are only asking for something to back it up beyond a "general" number...
It goes back to me advocating zeroing your rifle .25 MOA to .5 MOA left of center. I take up a lot of the spin drift deviation and can simply say, the "Lowlight Formula" for Spin Drift is to zero .36 MOA left of center at 100 yards"... why .3 MOA, because based on my extensive experience and success in field shooting I find .36 MOA at 100 yards satisfies 89% of the shooters in the western hemisphere with everything from a 308 to a 338 as well works well in the metric system... now prove my Formula doesn't work ?
I'll say, if someone of note is scared off by this and I personally don't see it as a cat fight, then the information they are bringing to the table is weak at best and probably falls in the "it works for me" category.
Otherwise with success and solid foundation in their reasoning there is no fight ? or debate.
There are tons of things that "work for me" in field, how I carry a ruck and can move farther and faster than guys twice my size. Does that mean I can explain it to someone else... no. so my reasoning by itself falls flat.
Hiding behind anything tells volumes in my opinion as does being scared away from debate, as no one is getting ugly, people are only asking for something to back it up beyond a "general" number...
It goes back to me advocating zeroing your rifle .25 MOA to .5 MOA left of center. I take up a lot of the spin drift deviation and can simply say, the "Lowlight Formula" for Spin Drift is to zero .36 MOA left of center at 100 yards"... why .3 MOA, because based on my extensive experience and success in field shooting I find .36 MOA at 100 yards satisfies 89% of the shooters in the western hemisphere with everything from a 308 to a 338 as well works well in the metric system... now prove my Formula doesn't work ?
Re: Spindrift Calculation??
Certainly not scared of anyone here I posted what my findings were and moved on. No need to argue on this. My data is hardly the be all and end all of things. Just what I see. I would love to hear form others who have findings who have not posted yet.
Certainly not scared of anyone here I posted what my findings were and moved on. No need to argue on this. My data is hardly the be all and end all of things. Just what I see. I would love to hear form others who have findings who have not posted yet.
Re: Spindrift Calculation??
Hypothetically speaking;
Would the spin drift effect diminish on a worn out barrel, or one with shallower rifling grooves? and.....
Is there a variation in spin drift based on the rate of twist?
ie more SD in faster twist
Hypothetically speaking;
Would the spin drift effect diminish on a worn out barrel, or one with shallower rifling grooves? and.....
Is there a variation in spin drift based on the rate of twist?
ie more SD in faster twist
Re: Spindrift Calculation??
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Archer</div><div class="ubbcode-body">Hypothetically speaking;
Would the spin drift effect diminish on a worn out barrel, or one with shallower rifling grooves? and.....
Is there a variation in spin drift based on the rate of twist?
ie more SD in faster twist </div></div>
it just depends
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Archer</div><div class="ubbcode-body">Hypothetically speaking;
Would the spin drift effect diminish on a worn out barrel, or one with shallower rifling grooves? and.....
Is there a variation in spin drift based on the rate of twist?
ie more SD in faster twist </div></div>
it just depends
Re: Spindrift Calculation??
Lowlight is as right as anything I can come up with. "Lost in the wind..." seems to be the operative term here.
I prefer "background/white noise", but these are all just different names for the same 1/2-1MOA of unmeasurable or unpredictable trajectory perturbations that no amount of calc can account for in any realtime exercise.
I am a retired computer programmer, and I have a very healthy respect for the capabilities of computers and programs. But the garbage coming out can only be as precise as the garbage going in, and let's face it folks, air is an essentially transparent medium. You can't see the wind under normal conditions, only its consequences, which are, by definition, after the fact.
The wind doesn't figure directly in spindrift, but the vaguaries of the wind are almost certainly and always going to present more inaccuracy than spindrift can.
If you want to crank in a small allowance for expected spindrift, then have at it; but really, I don't think it's going to turn a miss into a hit with enough certainty to be of any practical use.
Greg
Lowlight is as right as anything I can come up with. "Lost in the wind..." seems to be the operative term here.
I prefer "background/white noise", but these are all just different names for the same 1/2-1MOA of unmeasurable or unpredictable trajectory perturbations that no amount of calc can account for in any realtime exercise.
I am a retired computer programmer, and I have a very healthy respect for the capabilities of computers and programs. But the garbage coming out can only be as precise as the garbage going in, and let's face it folks, air is an essentially transparent medium. You can't see the wind under normal conditions, only its consequences, which are, by definition, after the fact.
The wind doesn't figure directly in spindrift, but the vaguaries of the wind are almost certainly and always going to present more inaccuracy than spindrift can.
If you want to crank in a small allowance for expected spindrift, then have at it; but really, I don't think it's going to turn a miss into a hit with enough certainty to be of any practical use.
Greg
Re: Spindrift Calculation??
hhmmmm... how to word some of this politely. Some shooters here are NOT shooting long range when coming up with their thoughts on spin drift. Here are some handrails to apply to the thinking.
1. SD exists practically at all ranges, it MUST be accounted for and applied in the last 25% of the supersonic range of the shot. SSR is defined as the range at which the bullet transitions to < 1125 fps, corrected for the air conditions as they exist.
2. Bore groove depth becoming shallower will ENHANCE the SD effect. Here's why, what happens when the bore becomes eroded to the point where accuracy is affected? The groups suffer, correct? If the group size is suffering, the bullet is not flying attitude correct. If the bullet isn't flying attitude correct the bullet is ALWAYS yawing and pitching more than it should be yawing and pitching. When that happens more of the bullets "footprint" is presented to the resisting air and the factors that cause SD are enhanced = greater spin drift.
Here is a scenario that I witnessed at a shoot in Idaho where several memebers of a special operations unit were evaluating the Cheytac ABC for purchase by their units. I was discussing with them the cost savings alone value of NOT shooting 5-20 cartridges every 100 yards from 100 - 2400 yards (their method at the time), the range time, the loss of man hour training time etc, vs. using the ABC to do the elevation and windage settings.
We "zeroed" (meaning, tuned the guns to the computers, measured the MV for each rifle and input the correct air conditions into each gun/computer setup before shooting. We then went from 500 to 2000 yards with their M88PIP .50 cal rifles. We were shooting military loaded AMAX match ammo (yes it did exist).
At 2000 yards the winds were measured at 2-3 mph from 5 o'clock.
The WIND correction based on that data is RIGHT windage 0.50 Minutes of Angle. That's dialing into the wind 2 clicks, not much.
BUT, the spin drift correction at that range for that bullet and met conditions is LEFT 1.75 MOA. The Coriolis correction for that shot is LEFT .75 MOA, for a combined total of LEFT 2.50 MOA, or roughly 50" DOWNWIND, a left correction for a right to left wind. Combined with the initial error of 0.50 MOA or about 10" right, that would have resulted in a 60" error on the target.
Results of live rounds fired? X3 shots, X 4 guns, X and 10 rings on the 1000 yd, bull with 2 shots into the 9 rings, LOW on the target. Additional results, multiple ABCs sold over the years based on budget effect along.
SD exists, get off of the KD ranges, get into the last 25% of the supersonic range of your gun. Still a fun subject to talk about. Oh, and don't just shoot a few bullets, do cumulative testing over time.
Isaiah 6:8
Trigger
hhmmmm... how to word some of this politely. Some shooters here are NOT shooting long range when coming up with their thoughts on spin drift. Here are some handrails to apply to the thinking.
1. SD exists practically at all ranges, it MUST be accounted for and applied in the last 25% of the supersonic range of the shot. SSR is defined as the range at which the bullet transitions to < 1125 fps, corrected for the air conditions as they exist.
2. Bore groove depth becoming shallower will ENHANCE the SD effect. Here's why, what happens when the bore becomes eroded to the point where accuracy is affected? The groups suffer, correct? If the group size is suffering, the bullet is not flying attitude correct. If the bullet isn't flying attitude correct the bullet is ALWAYS yawing and pitching more than it should be yawing and pitching. When that happens more of the bullets "footprint" is presented to the resisting air and the factors that cause SD are enhanced = greater spin drift.
Here is a scenario that I witnessed at a shoot in Idaho where several memebers of a special operations unit were evaluating the Cheytac ABC for purchase by their units. I was discussing with them the cost savings alone value of NOT shooting 5-20 cartridges every 100 yards from 100 - 2400 yards (their method at the time), the range time, the loss of man hour training time etc, vs. using the ABC to do the elevation and windage settings.
We "zeroed" (meaning, tuned the guns to the computers, measured the MV for each rifle and input the correct air conditions into each gun/computer setup before shooting. We then went from 500 to 2000 yards with their M88PIP .50 cal rifles. We were shooting military loaded AMAX match ammo (yes it did exist).
At 2000 yards the winds were measured at 2-3 mph from 5 o'clock.
The WIND correction based on that data is RIGHT windage 0.50 Minutes of Angle. That's dialing into the wind 2 clicks, not much.
BUT, the spin drift correction at that range for that bullet and met conditions is LEFT 1.75 MOA. The Coriolis correction for that shot is LEFT .75 MOA, for a combined total of LEFT 2.50 MOA, or roughly 50" DOWNWIND, a left correction for a right to left wind. Combined with the initial error of 0.50 MOA or about 10" right, that would have resulted in a 60" error on the target.
Results of live rounds fired? X3 shots, X 4 guns, X and 10 rings on the 1000 yd, bull with 2 shots into the 9 rings, LOW on the target. Additional results, multiple ABCs sold over the years based on budget effect along.
SD exists, get off of the KD ranges, get into the last 25% of the supersonic range of your gun. Still a fun subject to talk about. Oh, and don't just shoot a few bullets, do cumulative testing over time.
Isaiah 6:8
Trigger
Re: Spindrift Calculation??
Dean,
I hear what you're saying, and I respect you for you knowledge of the subject, but I disagree. I've never shot to 2000 yards as 1600 meters is my furthest. I've done a lot of long range shooting out west and I've never seen (ever, ever) a constant x mph wind blowing in one direction for the entire path of the bullet flight. It just doesn't exist in my book.
I know you're tied into the ABC program, and I'm sure it's worth it's weight in gold in a controlled testing environment. Having said that it's possibly a practical tool (the ballistic program only) I can use on a long range hunt or shoot to get me in the ball park like most of the better ballistic programs.
Any amount of SD will be lost in the wind at long ranges when you factor in all of the other variables we've talked about. Cross winds at different speeds, ranges and altitudes will cancel out any type of spin drift corrections you wanted to make. If you look at the factors of my ground hog hunt I posted earlier, there is no way to say I should factor in an x amount of correction for spin drift and x amount for wind.
At the end of the day, you can say you factored in an x amount of correction for SD, but in a real world of a 1K to 2K shot with variables wind conditions any SD will still be lost in the winds and compensated for in windage corrections.
I will agree I could always start off with some type of base point correction for SD, but I still have to correct for all the other variables. Whether I start out of with a base correction or not, I'm still factoring all of the other variables and SD is still lost in the wind.
Dean,
I hear what you're saying, and I respect you for you knowledge of the subject, but I disagree. I've never shot to 2000 yards as 1600 meters is my furthest. I've done a lot of long range shooting out west and I've never seen (ever, ever) a constant x mph wind blowing in one direction for the entire path of the bullet flight. It just doesn't exist in my book.
I know you're tied into the ABC program, and I'm sure it's worth it's weight in gold in a controlled testing environment. Having said that it's possibly a practical tool (the ballistic program only) I can use on a long range hunt or shoot to get me in the ball park like most of the better ballistic programs.
Any amount of SD will be lost in the wind at long ranges when you factor in all of the other variables we've talked about. Cross winds at different speeds, ranges and altitudes will cancel out any type of spin drift corrections you wanted to make. If you look at the factors of my ground hog hunt I posted earlier, there is no way to say I should factor in an x amount of correction for spin drift and x amount for wind.
At the end of the day, you can say you factored in an x amount of correction for SD, but in a real world of a 1K to 2K shot with variables wind conditions any SD will still be lost in the winds and compensated for in windage corrections.
I will agree I could always start off with some type of base point correction for SD, but I still have to correct for all the other variables. Whether I start out of with a base correction or not, I'm still factoring all of the other variables and SD is still lost in the wind.
Re: Spindrift Calculation??
Jeff,
I agree with your note on multiple winds. Gotta address them, I just look at this whole SD and Coriolis thing as this. If there is anything that I CAN analyze and eliminate mathematically, I would rather NOT assume something is missing in the wind. There are ways of analyzing air temps, terrain, changes in BP pressure, direction of wind in relation to terrain mass flow and making a very accurate assessment of downrange winds.
If one doesn't take the time to keep the "group size" capability of the gun centered up over the target by eliminating Coriolis and SD, then what good is there in writing down historical information on shots already taken?
My point of view also is entirely from only having the ability to take minimal shots and each additional shot is likely to shorten one's life expectancy. There is some room for correction based on time, reaction time, etc. In the world I am used to, there are no sighting shots. Though something like a "sighting shot" can be done.
The example that I provided above is a good example. There was a long period of silence after those rounds were downrange, alot of note taking, and for us, some serious high fiving.
Jeff,
I agree with your note on multiple winds. Gotta address them, I just look at this whole SD and Coriolis thing as this. If there is anything that I CAN analyze and eliminate mathematically, I would rather NOT assume something is missing in the wind. There are ways of analyzing air temps, terrain, changes in BP pressure, direction of wind in relation to terrain mass flow and making a very accurate assessment of downrange winds.
If one doesn't take the time to keep the "group size" capability of the gun centered up over the target by eliminating Coriolis and SD, then what good is there in writing down historical information on shots already taken?
My point of view also is entirely from only having the ability to take minimal shots and each additional shot is likely to shorten one's life expectancy. There is some room for correction based on time, reaction time, etc. In the world I am used to, there are no sighting shots. Though something like a "sighting shot" can be done.
The example that I provided above is a good example. There was a long period of silence after those rounds were downrange, alot of note taking, and for us, some serious high fiving.
Re: Spindrift Calculation??
I continue to love how we go from talking about 1 MOA at 1000 yards to 2000 yard shots were the SD becomes much biggger.
How about sticking to 1 MOA at 1000 yards... that number is the one we are talking about... we all get it, different animal beyond. The contention is the 1 MOA at 1000 yards.
I continue to love how we go from talking about 1 MOA at 1000 yards to 2000 yard shots were the SD becomes much biggger.
How about sticking to 1 MOA at 1000 yards... that number is the one we are talking about... we all get it, different animal beyond. The contention is the 1 MOA at 1000 yards.
Re: Spindrift Calculation??
Dean, what is the percentage of achieving a 1st round hit at 1800m using the ABC program as opposed to not using it ?
Also, how does the size and weight of the bullet compare, say the 408CT to the 175gr is it proportional or completely varied ?
Basically are are well really discussing Apples and Apples or Apples and Oranges when we move from 1000 yard to 2000. How does a specialized system like a $12k rifle and $5k ballistic program translate to shooting a 308 at 1000 yards in regards to SD... you know the last 25% of that system, as opposed to the ELR application... cause I think plenty of people are off the KD inside 1000 yards as not everyone is interested in ELR or has access to its ranges or application.
Dean, what is the percentage of achieving a 1st round hit at 1800m using the ABC program as opposed to not using it ?
Also, how does the size and weight of the bullet compare, say the 408CT to the 175gr is it proportional or completely varied ?
Basically are are well really discussing Apples and Apples or Apples and Oranges when we move from 1000 yard to 2000. How does a specialized system like a $12k rifle and $5k ballistic program translate to shooting a 308 at 1000 yards in regards to SD... you know the last 25% of that system, as opposed to the ELR application... cause I think plenty of people are off the KD inside 1000 yards as not everyone is interested in ELR or has access to its ranges or application.
Re: Spindrift Calculation??
Lowlight,
Good questions, but first, the 1 MOA at 1000 yards issue. That is ONLY for 168, 173 SB, 173 SMK, 185 Lapua FMJBT and Scenar and other NON controlled spin bullets. You see, the controlled spin of the LRBT bullets, when it' working corrects about 87% on the average of spin characteristics. For example:
All of these are 1000 yard spin drift data in INCHES:
308 cal / 220 gr. SMK: 7.75"
308 cal / 190 gr. SMK: 155 gr. Palma SMK : 12.75"
308 cal / 190 gr. LRBT: J40 Match: 3.00"
308 cal / 173 gr. Special Ball: 11.50"
for comparison:
408 Cheytac:
Lowlight,
Good questions, but first, the 1 MOA at 1000 yards issue. That is ONLY for 168, 173 SB, 173 SMK, 185 Lapua FMJBT and Scenar and other NON controlled spin bullets. You see, the controlled spin of the LRBT bullets, when it' working corrects about 87% on the average of spin characteristics. For example:
All of these are 1000 yard spin drift data in INCHES:
308 cal / 220 gr. SMK: 7.75"
308 cal / 190 gr. SMK: 155 gr. Palma SMK : 12.75"
308 cal / 190 gr. LRBT: J40 Match: 3.00"
308 cal / 173 gr. Special Ball: 11.50"
for comparison:
408 Cheytac:
Re: Spindrift Calculation??
Sorry, more...
408 Cheytac: 1.9"
375 / 408 Cheytac: 0.87"
5.56mm M193 Ball: 23.0" alot huh?
338 Lapua / 300 gr. SMK: 6.5"
So, no there is no standard MOA at a certain range. Many factors come into play.
As for controlled spin bullets, here's the list:
50 cal T50 (not my idea on the name), 773 gr. Hooker/LRBT
408 Cheytac, bullets made by Hooker and Cheytac
375/408, bullets made by Hooker and Cheytac
338 270 gr. and to a lesser degree the 250 gr. LRBT and Hooker bullets.
.308 caliber 190 J40 Match by LRBT / Hooker
and a few others. These controlled spin bullets do not like tight bore barrels, like the kind that "squeeze" jacketed bullets for more accuracy. This over stresses the solid and it leaves the crown with alot of torque stored in it, causing yawing and pitching, sometimes it settles down, most times the groups double over the normal size of a matched bullet barrel setup.
The good news about that, is that solids don't need a "high speed" tight bore barrel to work, but they do need a specific dimension in the lands and grooves (depth of engraving, width of the lands and grooves for example).
As to the other question about 1800 m with the ABC. Well without a good computer program, you're simply guessing. The ABC integrates 7 horizontal and 5 vertical corrections to the elevation and windage and they do it in the correct sequence. My personal testing of the other programs that are out there is that they execute in the wrong sequence, resulting in errors. That's irregardless of the fact that the other programs use a singular BC value that is an average, or maybe 3 or 5 different BCs. All of that works pretty well, again the problem becomes when you reach into that last 25% of the supersonic range.
More tomorrow, gotta head to the hospital and practice my new career. Later guys, it's very cool that this string goes this long. On a few other sites, it was tossed by the site's "gurus" as being a non-entity or they brow beat those that thought it has merit. Ultimately it's about how much error you allow yourself. Error budget sniping, that's what it's all about.
Later guys,
Trigger
PS,, thanks for the support that you are sending on my personal issue right now. Those notes make the day a bit better, sitting on my horses takes up about 20% of the rest, and God gets credit for the rest of the peace that I get, little as it may be.
Sorry, more...
408 Cheytac: 1.9"
375 / 408 Cheytac: 0.87"
5.56mm M193 Ball: 23.0" alot huh?
338 Lapua / 300 gr. SMK: 6.5"
So, no there is no standard MOA at a certain range. Many factors come into play.
As for controlled spin bullets, here's the list:
50 cal T50 (not my idea on the name), 773 gr. Hooker/LRBT
408 Cheytac, bullets made by Hooker and Cheytac
375/408, bullets made by Hooker and Cheytac
338 270 gr. and to a lesser degree the 250 gr. LRBT and Hooker bullets.
.308 caliber 190 J40 Match by LRBT / Hooker
and a few others. These controlled spin bullets do not like tight bore barrels, like the kind that "squeeze" jacketed bullets for more accuracy. This over stresses the solid and it leaves the crown with alot of torque stored in it, causing yawing and pitching, sometimes it settles down, most times the groups double over the normal size of a matched bullet barrel setup.
The good news about that, is that solids don't need a "high speed" tight bore barrel to work, but they do need a specific dimension in the lands and grooves (depth of engraving, width of the lands and grooves for example).
As to the other question about 1800 m with the ABC. Well without a good computer program, you're simply guessing. The ABC integrates 7 horizontal and 5 vertical corrections to the elevation and windage and they do it in the correct sequence. My personal testing of the other programs that are out there is that they execute in the wrong sequence, resulting in errors. That's irregardless of the fact that the other programs use a singular BC value that is an average, or maybe 3 or 5 different BCs. All of that works pretty well, again the problem becomes when you reach into that last 25% of the supersonic range.
More tomorrow, gotta head to the hospital and practice my new career. Later guys, it's very cool that this string goes this long. On a few other sites, it was tossed by the site's "gurus" as being a non-entity or they brow beat those that thought it has merit. Ultimately it's about how much error you allow yourself. Error budget sniping, that's what it's all about.
Later guys,
Trigger
PS,, thanks for the support that you are sending on my personal issue right now. Those notes make the day a bit better, sitting on my horses takes up about 20% of the rest, and God gets credit for the rest of the peace that I get, little as it may be.
Re: Spindrift Calculation??
Wow..thats some good shit there Dean..Thanks and best of luck in your new career.
Wow..thats some good shit there Dean..Thanks and best of luck in your new career.
Re: Spindrift Calculation??
Dean,
I am going to explore some information I have, and I don't know how much 308 you shoot, but the numbers go against my Downrange data -- and I shoot a ton of 308... almost exclusively.
I know a lot of people shoot 155gr bullets specifically for the down range benefits, and to say it 'drifts' 13" at 1000 yards is a little beyond most people's experience with the round. A drift that significant would show up in the wind and it's definitely a wind cheater compared to a 173gr.
Hooker / LRB being able to go from 12" to 3" is a pretty amazing feat, I don't doubt the benefits, but that is pretty significant enough to ask why with their high BCs would anyone advocate any other bullet, which might be the point.
As well the 173gr bullet, having used them for a very long time, I don't see them being better than a 155gr like that.
Anyway, I appreciate the post, I will say, my software which calculates SD as well as my own experience downrange put the drift for a 308 around .7, which would be inline with your 220gr bullet.. however i think you might mean that for a 300WM, not so much a 308. Same with the 190gr. Also my program requires me to include the twist which you didn't include.
But I will look at the numbers, and see how it compares to my downrange experience... so no one things I am being overly obstinate, my findings are closer to .7 with a 175gr 1-10 twist and with my 170gr and 1-11 I see as little as .5, but it is a very fast, good flying round at distance.
The numbers not withstanding, I think downrange experience has to account for something.
Dean,
I am going to explore some information I have, and I don't know how much 308 you shoot, but the numbers go against my Downrange data -- and I shoot a ton of 308... almost exclusively.
I know a lot of people shoot 155gr bullets specifically for the down range benefits, and to say it 'drifts' 13" at 1000 yards is a little beyond most people's experience with the round. A drift that significant would show up in the wind and it's definitely a wind cheater compared to a 173gr.
Hooker / LRB being able to go from 12" to 3" is a pretty amazing feat, I don't doubt the benefits, but that is pretty significant enough to ask why with their high BCs would anyone advocate any other bullet, which might be the point.
As well the 173gr bullet, having used them for a very long time, I don't see them being better than a 155gr like that.
Anyway, I appreciate the post, I will say, my software which calculates SD as well as my own experience downrange put the drift for a 308 around .7, which would be inline with your 220gr bullet.. however i think you might mean that for a 300WM, not so much a 308. Same with the 190gr. Also my program requires me to include the twist which you didn't include.
But I will look at the numbers, and see how it compares to my downrange experience... so no one things I am being overly obstinate, my findings are closer to .7 with a 175gr 1-10 twist and with my 170gr and 1-11 I see as little as .5, but it is a very fast, good flying round at distance.
The numbers not withstanding, I think downrange experience has to account for something.
Re: Spindrift Calculation??
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Where's that 1000y tunnel we can truly test this stuff in???</div></div>
If you build it, we will come...
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Where's that 1000y tunnel we can truly test this stuff in???</div></div>
If you build it, we will come...
Re: Spindrift Calculation??
Dean, thanks for sharring all this. No doubt your the expert on this.
I am no expert on this but went back over the log books after I had long talk on this with Frank yesterday.
I put up it seemed like about a minute of drift at 1000 yards with Scenars out of a 1x11 twist bbl. Now understand this when I say 1 moa it could be .75 moa or 1.25 because its just not possible for me to call wind finer than that. Not perfect science here. Now i have switched to 1x12 twist and it seems like its closer to .75 (plus or minus .25moa at best again)
I have shot a bunch of 77 grain bullets at 1000 yards and have not noticed that much drift. I would have guessed slightly more drift than 155s. I dont have log books like I do with my 308 because the 77s are more of a fun shoot at 1000 yards. I only keep come ups as hits at 1000 with this are just to do so, not compete.
On most occassions for me, the drift is lost in wind as already said.
Not perfect science on my part, but it works for me. Sure would love to learn how these numbers are come up with
Dean, thanks for sharring all this. No doubt your the expert on this.
I am no expert on this but went back over the log books after I had long talk on this with Frank yesterday.
I put up it seemed like about a minute of drift at 1000 yards with Scenars out of a 1x11 twist bbl. Now understand this when I say 1 moa it could be .75 moa or 1.25 because its just not possible for me to call wind finer than that. Not perfect science here. Now i have switched to 1x12 twist and it seems like its closer to .75 (plus or minus .25moa at best again)
I have shot a bunch of 77 grain bullets at 1000 yards and have not noticed that much drift. I would have guessed slightly more drift than 155s. I dont have log books like I do with my 308 because the 77s are more of a fun shoot at 1000 yards. I only keep come ups as hits at 1000 with this are just to do so, not compete.
On most occassions for me, the drift is lost in wind as already said.
Not perfect science on my part, but it works for me. Sure would love to learn how these numbers are come up with
Re: Spindrift Calculation??
Been avoiding this topic lately because of the sceptics that try to slam the ones who want to acknowledge SD and other somewhat minor effect of bullet flight. Glad to see some truely good input going on here.
I defintly account for spin drift and take into consirderation corralis effect at long range. 1000yards+.
My info:
With my FN SPR 300WSM was doing about 1 moa at 1000yrds with 190SMK and 1:10twist. Others rifles, to hard for me to say with out trying it more in good conditions multiple times.
Been avoiding this topic lately because of the sceptics that try to slam the ones who want to acknowledge SD and other somewhat minor effect of bullet flight. Glad to see some truely good input going on here.
I defintly account for spin drift and take into consirderation corralis effect at long range. 1000yards+.
My info:
With my FN SPR 300WSM was doing about 1 moa at 1000yrds with 190SMK and 1:10twist. Others rifles, to hard for me to say with out trying it more in good conditions multiple times.
Re: Spindrift Calculation??
10 pages in I will try to go back to the basics of what we are talking about for the readers.
My understanding of what causes spin drift.
The bullet is dropping through the air because of gravity and spinning caused by the rifling twist in barrels. When the bullet is dropping is causes a higher pressure on the bottom side of the bullet compared to the top. This pressure diffrencial cause the bullet to drift while spinning though the air. More drag on the bottom of the bullet while spinning than the top because of the pressure differential. Get that bullet to fly perfectly nosed into its flight path and the effect is minamalized. An added effect is BC stays up.
Used to be some good sites and info on this I had in my favorites. They are eaither no more or I lost them.
10 pages in I will try to go back to the basics of what we are talking about for the readers.
My understanding of what causes spin drift.
The bullet is dropping through the air because of gravity and spinning caused by the rifling twist in barrels. When the bullet is dropping is causes a higher pressure on the bottom side of the bullet compared to the top. This pressure diffrencial cause the bullet to drift while spinning though the air. More drag on the bottom of the bullet while spinning than the top because of the pressure differential. Get that bullet to fly perfectly nosed into its flight path and the effect is minamalized. An added effect is BC stays up.
Used to be some good sites and info on this I had in my favorites. They are eaither no more or I lost them.
Re: Spindrift Calculation??
Quick question, what happens if I turn the rifle upside down and shoot... will the drift go in the opposite direction ?
Quick question, what happens if I turn the rifle upside down and shoot... will the drift go in the opposite direction ?
Re: Spindrift Calculation??
Montana,,, you nailed it. It's that simple.
IsleofGough... never shot a bullet backwards down the bore? Doesn't hurt a thing, as long as the crowns in good shape, accuracy is pretty good, DAMN hard on wild boar, a 220 gr. SMK out of a 300 mag going backwards...mmm mmmm mmm ... bacon.
Matchking in to semi wadcutter with a flip of the tip. Somewhere around here I have some pics of these rounds, built for "wild boar" shooting. Drops them hard. Gotta slow down the velocity to around 2000 fps or so or the burning powder gas will invade the tip of the reversed SMK and shred the bullet in the barrel. A Lapua 185 gr. FMJBT turned around is a better way to go. Still, keep velocity around 2600 fps or less and the accuracy is good. This is only a 400 yard bullet at best but increases the "shock" to the system and very much decreases to life to lifeless time on the target.
Later,
Trig
Montana,,, you nailed it. It's that simple.
IsleofGough... never shot a bullet backwards down the bore? Doesn't hurt a thing, as long as the crowns in good shape, accuracy is pretty good, DAMN hard on wild boar, a 220 gr. SMK out of a 300 mag going backwards...mmm mmmm mmm ... bacon.
Matchking in to semi wadcutter with a flip of the tip. Somewhere around here I have some pics of these rounds, built for "wild boar" shooting. Drops them hard. Gotta slow down the velocity to around 2000 fps or so or the burning powder gas will invade the tip of the reversed SMK and shred the bullet in the barrel. A Lapua 185 gr. FMJBT turned around is a better way to go. Still, keep velocity around 2600 fps or less and the accuracy is good. This is only a 400 yard bullet at best but increases the "shock" to the system and very much decreases to life to lifeless time on the target.
Later,
Trig
Re: Spindrift Calculation??
Magnus Effect, if anyone wants to do more research on this simple fact of flight.
http://www.nennstiel-ruprecht.de/bullfly/fig9.htm
This web site has lots of other excellent info on it.
Magnus Effect, if anyone wants to do more research on this simple fact of flight.
http://www.nennstiel-ruprecht.de/bullfly/fig9.htm
This web site has lots of other excellent info on it.
Re: Spindrift Calculation??
I did a bad thing this afternoon.
I am down at Raton to shoot the Sporting Rifle Match and after a few practice rounds before tomorrow's competition Chuck tells me there is a 1700 yard target, size 14" X 20" off to the side. So, really quick I move my stuff and pull a number out for an elevation. Without adjusting for any of environmental conditions I grab 17 Mils off my PDA for my 7WSM shooting a 175gr bullet.
The wind we figured, 2 - 3 Mph first coming from the left but then switching up from the right based on our observations.
I let a round go and my dope was too high, but wind was good. I read my Mil adjustments off the scope and come down a Mil and Half and hit just off the left of the target... I make the correction, making sure I had my hold right, and after the guys moved some grass from in front of us, and what do you know with the wind correction from the computer I get a hit. The computer said .8 and I .7 mils on the scope... nothing else and hit the target.
Funny things, everyone else was hitting with their 338 too.. just what the wind said. I asked Mike the match director how much spindrift he was using and he said, "what is that" ? I said never mind, you hit it. He said ya, I shot, saw the splash corrected and hit the target what else do I need" I said, Nothing... (Mike doesn't have a computer or internet)
I know, I'm stirring the pot... but I did see Jeff Badley do the same thing with his 7WSM at 1997 yards... must be the caliber or something.
After I corrected the conditions in my computer it was much better, originally I had Denver stuff in there and not Raton, 1000 feet difference and temperature was different too.
I did a bad thing this afternoon.
I am down at Raton to shoot the Sporting Rifle Match and after a few practice rounds before tomorrow's competition Chuck tells me there is a 1700 yard target, size 14" X 20" off to the side. So, really quick I move my stuff and pull a number out for an elevation. Without adjusting for any of environmental conditions I grab 17 Mils off my PDA for my 7WSM shooting a 175gr bullet.
The wind we figured, 2 - 3 Mph first coming from the left but then switching up from the right based on our observations.
I let a round go and my dope was too high, but wind was good. I read my Mil adjustments off the scope and come down a Mil and Half and hit just off the left of the target... I make the correction, making sure I had my hold right, and after the guys moved some grass from in front of us, and what do you know with the wind correction from the computer I get a hit. The computer said .8 and I .7 mils on the scope... nothing else and hit the target.
Funny things, everyone else was hitting with their 338 too.. just what the wind said. I asked Mike the match director how much spindrift he was using and he said, "what is that" ? I said never mind, you hit it. He said ya, I shot, saw the splash corrected and hit the target what else do I need" I said, Nothing... (Mike doesn't have a computer or internet)
I know, I'm stirring the pot... but I did see Jeff Badley do the same thing with his 7WSM at 1997 yards... must be the caliber or something.
Re: Spindrift Calculation??
Lowlight,
I'm also in Raton, shooting the Spirit of America match on the George Tubb range. How long will you be in town? I'll be here all week. If you'd like to grab chow some night, shoot me an email: [email protected] with your phone number or something and we'll set it up.
I'm seeing many familiar faces out here from the fullbore world. I'm always up for meeting new people, and talking about different kinds of shooting.
-Bryan
Lowlight,
I'm also in Raton, shooting the Spirit of America match on the George Tubb range. How long will you be in town? I'll be here all week. If you'd like to grab chow some night, shoot me an email: [email protected] with your phone number or something and we'll set it up.
I'm seeing many familiar faces out here from the fullbore world. I'm always up for meeting new people, and talking about different kinds of shooting.
-Bryan
Re: Spindrift Calculation??
Guys, i was just in Raton for the day... I'm not around anymore.
I will be in Pueblo next weekend for the Vickers class, that is the closest I will be unless you pass through Denver.
Sorry, just a quick one day thing there.
Oh, and actual yardage on the target given to me after the fact was 1684 yards... so not quite 1700.
Guys, i was just in Raton for the day... I'm not around anymore.
I will be in Pueblo next weekend for the Vickers class, that is the closest I will be unless you pass through Denver.
Sorry, just a quick one day thing there.
Oh, and actual yardage on the target given to me after the fact was 1684 yards... so not quite 1700.
Re: Spindrift Calculation??
We compensate for spin drift, doesnt matter on closer range by try 2100yards and not compensate for it you will miss! My smith has a 2 ranges with steel all the way out to 2100yards, starting at 600yards! Conrad MT, is where we are located come on up!
We compensate for spin drift, doesnt matter on closer range by try 2100yards and not compensate for it you will miss! My smith has a 2 ranges with steel all the way out to 2100yards, starting at 600yards! Conrad MT, is where we are located come on up!
Re: Spindrift Calculation??
I think its real. In a dead calm (I think)my 168 gr 308 moves right 1/4-1/2 MOA at 1000 yds
I think its real. In a dead calm (I think)my 168 gr 308 moves right 1/4-1/2 MOA at 1000 yds
Re: Spindrift Calculation??
This is what Arthur Pejsa says in new exact small arms ballistics page 88
1: The effect varies based on the center of gravity vs. the center of pressure of the bullet. It must be empirically measured like BC
2: According to army drift tables the effect is about equal to the Coriolis effect
3: Given a left hand twist barrel it would tend to cancel out the Coriolis effect in the northern hemisphere.
This is what Arthur Pejsa says in new exact small arms ballistics page 88
1: The effect varies based on the center of gravity vs. the center of pressure of the bullet. It must be empirically measured like BC
2: According to army drift tables the effect is about equal to the Coriolis effect
3: Given a left hand twist barrel it would tend to cancel out the Coriolis effect in the northern hemisphere.
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