- Thread starter DaveV
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Re: Spin drift
Aw, chit, here we go! There was a topic about this many moons ago that got everybody fired up. Basically, under 1000 yards, don't worry about it. Depending on the bullet, twist rate and speed, it will drift to the right anywhere from 2"-5" at 1K.
Aw, chit, here we go! There was a topic about this many moons ago that got everybody fired up. Basically, under 1000 yards, don't worry about it. Depending on the bullet, twist rate and speed, it will drift to the right anywhere from 2"-5" at 1K.
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">Aw, chit, here we go! There was a topic about this many moons ago that got everybody fired up. Basically, under 1000 yards, don't worry about it. Depending on the bullet, twist rate and speed, it will drift to the right anywhere from 2"-5" at 1K. </div></div>
Sorry Chad, I searched and didn't see anything useful. I don't want to open up a flamer. Just curious if this is used beyond the ballistic programs.
I'm looking more at 1200-1500
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">Aw, chit, here we go! There was a topic about this many moons ago that got everybody fired up. Basically, under 1000 yards, don't worry about it. Depending on the bullet, twist rate and speed, it will drift to the right anywhere from 2"-5" at 1K. </div></div>
Sorry Chad, I searched and didn't see anything useful. I don't want to open up a flamer. Just curious if this is used beyond the ballistic programs.
I'm looking more at 1200-1500
Re: Spin drift
Go Here: http://www.google.com/cse/home?cx=010955838166721108978:qcbx5qqy10o&hl=en
Type in spin drift, and you will get all the info you want. I started a spin drift thread several years ago, and it turned into about 7 pages of debate, but did have some good info in it. I think this old thread got deleted when they did the upgrade. But it had good info in it.
Go Here: http://www.google.com/cse/home?cx=010955838166721108978:qcbx5qqy10o&hl=en
Type in spin drift, and you will get all the info you want. I started a spin drift thread several years ago, and it turned into about 7 pages of debate, but did have some good info in it. I think this old thread got deleted when they did the upgrade. But it had good info in it.
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">
I started a spin drift thread several years ago, and it turned into about 7 pages of debate, but did have some good info in it. </div></div>
Me too. LOL
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">
I started a spin drift thread several years ago, and it turned into about 7 pages of debate, but did have some good info in it. </div></div>
Me too. LOL
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">Go Here: http://www.google.com/cse/home?cx=010955838166721108978:qcbx5qqy10o&hl=en
Type in spin drift, and you will get all the info you want. I started a spin drift thread several years ago, and it turned into about 7 pages of debate, but did have some good info in it. I think this old thread got deleted when they did the upgrade. But it had good info in it. </div></div>
Should have gone with the Google engine. How do you put the Genie back in the bottle?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">Go Here: http://www.google.com/cse/home?cx=010955838166721108978:qcbx5qqy10o&hl=en
Type in spin drift, and you will get all the info you want. I started a spin drift thread several years ago, and it turned into about 7 pages of debate, but did have some good info in it. I think this old thread got deleted when they did the upgrade. But it had good info in it. </div></div>
Should have gone with the Google engine. How do you put the Genie back in the bottle?
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">How do you put the Genie back in the bottle? </div></div>
Yes we need to do that. Like has been posted this topic has been covered many times. The last one ran over seven pages. Some people believe that they need to put it in to there dope and other do not. To each his own.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">How do you put the Genie back in the bottle? </div></div>
Yes we need to do that. Like has been posted this topic has been covered many times. The last one ran over seven pages. Some people believe that they need to put it in to there dope and other do not. To each his own.
Re: Spin drift
I guess my original question still stands. I'm not asking if one "should" calc for it. I asked, "<span style="text-decoration: underline">Do</span> you calc for it?" I'm not interested in reading any more opinions and tech sheets on the theory. My interest is in real world "do <span style="text-decoration: underline">you</span> use it?" and "have <span style="text-decoration: underline">you</span> seen emperical results from it?" Simple yes/no answers could be used without all the dick measuring flames. YMMV
Besides, I'm not the one who brought it up. It was the dude on the History channel
I guess my original question still stands. I'm not asking if one "should" calc for it. I asked, "<span style="text-decoration: underline">Do</span> you calc for it?" I'm not interested in reading any more opinions and tech sheets on the theory. My interest is in real world "do <span style="text-decoration: underline">you</span> use it?" and "have <span style="text-decoration: underline">you</span> seen emperical results from it?" Simple yes/no answers could be used without all the dick measuring flames. YMMV
Besides, I'm not the one who brought it up. It was the dude on the History channel
Re: Spin drift
...stalk in for a closer shot and don't worry about it.
...stalk in for a closer shot and don't worry about it.
Re: Spin drift
Dave, yes I do factor it in, but that's just me. Many here feel it is too little to worry about.
My .02
Dave, yes I do factor it in, but that's just me. Many here feel it is too little to worry about.
My .02
Re: Spin drift
think about it......
you torch off your pill and it spins out the end of your truck axle at a really really high rate of speed, something on the order of several magnitudes better than your maytag on spin cycle.....and the pill got small little groove thingies engraved in them from scraping its way down the truck axle....grabbing them air molecules, biting its way through the air as it flys to the target.....spinning and spinning ...to the right....so yeah the pill goes to the right.
so the savvy and salty just cant the scope 2* or 3* to connect the pills with the target at them 1000yd targets
think about it......
you torch off your pill and it spins out the end of your truck axle at a really really high rate of speed, something on the order of several magnitudes better than your maytag on spin cycle.....and the pill got small little groove thingies engraved in them from scraping its way down the truck axle....grabbing them air molecules, biting its way through the air as it flys to the target.....spinning and spinning ...to the right....so yeah the pill goes to the right.
so the savvy and salty just cant the scope 2* or 3* to connect the pills with the target at them 1000yd targets
Re: Spin drift
In ExBal it's actually "Shooter Drift" ... just saying.
In ExBal it's actually "Shooter Drift" ... just saying.
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">Aw, chit, here we go! There was a topic about this many moons ago that got everybody fired up. Basically, under 1000 yards, don't worry about it. Depending on the bullet, twist rate and speed,<span style="font-weight: bold"> it will drift to the right anywhere from 2"-5" at 1K</span>. </div></div>
Feck. My heartbeat covers 1/2 moa at this range. I can't tell if it's spin drift or shooting technique, or maybe a 1/4 value wind over 200 yards.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">Aw, chit, here we go! There was a topic about this many moons ago that got everybody fired up. Basically, under 1000 yards, don't worry about it. Depending on the bullet, twist rate and speed,<span style="font-weight: bold"> it will drift to the right anywhere from 2"-5" at 1K</span>. </div></div>
Feck. My heartbeat covers 1/2 moa at this range. I can't tell if it's spin drift or shooting technique, or maybe a 1/4 value wind over 200 yards.
G
Guest
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Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DaveV</div><div class="ubbcode-body"> I'm not asking if "<span style="text-decoration: underline">Do</span> you calc for it?" I'm not interested in reading any more opinions and tech sheets on the theory. My interest is in real world "do <span style="text-decoration: underline">you</span> use it?" and "have <span style="text-decoration: underline">you</span> seen emperical results from it?" Simple yes/no answers could be used without all the dick measuring flames.</div></div>
Everyone gets to the target their way. I zero at 100 then dial in my 1K dope and keep moving the top of the retical to the left (.308win throwing 175's) until I'm 3/4 to 1"(shooting for 7/8") to the left of the plum line I drew. For the 300wm throwing 208's it's between 1/2 an 5/8"'s(looking for 9/16"). It matters little what I do compared to everyone else, as no two folks shoot the same way. If you think you need 5 mins go for it, if you think you need 3 min's right thats OK as well. The target tells the story, no matter want the pre-amble is.
I've shot right beside a number of "Great" shooters an we were both looking/shooting at the same 0900 wind at 1K targets. He would have 3 minutes on, I would have 1.5 to 2.0" (and holding alittle) we both were in there. Then theres been times were the mirage was flat lines, I'd have nothing on and he would have between 1/2-3/4-1moa left,..we both were still in there. As long as your on target it matters little, what everyone else thinks, or is doing.
Both of my USO's are 1/2 IPHY both ways, on a good day I can hold 1/4" past 600yds, most days not.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DaveV</div><div class="ubbcode-body"> I'm not asking if "<span style="text-decoration: underline">Do</span> you calc for it?" I'm not interested in reading any more opinions and tech sheets on the theory. My interest is in real world "do <span style="text-decoration: underline">you</span> use it?" and "have <span style="text-decoration: underline">you</span> seen emperical results from it?" Simple yes/no answers could be used without all the dick measuring flames.</div></div>
Everyone gets to the target their way. I zero at 100 then dial in my 1K dope and keep moving the top of the retical to the left (.308win throwing 175's) until I'm 3/4 to 1"(shooting for 7/8") to the left of the plum line I drew. For the 300wm throwing 208's it's between 1/2 an 5/8"'s(looking for 9/16"). It matters little what I do compared to everyone else, as no two folks shoot the same way. If you think you need 5 mins go for it, if you think you need 3 min's right thats OK as well. The target tells the story, no matter want the pre-amble is.
I've shot right beside a number of "Great" shooters an we were both looking/shooting at the same 0900 wind at 1K targets. He would have 3 minutes on, I would have 1.5 to 2.0" (and holding alittle) we both were in there. Then theres been times were the mirage was flat lines, I'd have nothing on and he would have between 1/2-3/4-1moa left,..we both were still in there. As long as your on target it matters little, what everyone else thinks, or is doing.
Both of my USO's are 1/2 IPHY both ways, on a good day I can hold 1/4" past 600yds, most days not.
Re: Spin drift
Spin drift for a standard .308 at 1000 yards is in the same range as the value of a 1 mph full-value crosswind. Unless I'm pretty sure that there is no effective wind, I don't bother to hold for spin drift, as I am dubious about my ability to dope the wind to an accuracy of 1 mph.
Those who are shooting at extra-long ranges might wish to consider it.
Spin drift for a standard .308 at 1000 yards is in the same range as the value of a 1 mph full-value crosswind. Unless I'm pretty sure that there is no effective wind, I don't bother to hold for spin drift, as I am dubious about my ability to dope the wind to an accuracy of 1 mph.
Those who are shooting at extra-long ranges might wish to consider it.
Re: Spin drift
I try to adress every problem... If my shitty form costs me 1/2 MOA, and my shitty wind reading costs me 1/2 MOA, and spin drift costs me 1/2 MOA, why not try to adress them all?
SPIN DRIFT TOPIC! BRING IT!
I try to adress every problem... If my shitty form costs me 1/2 MOA, and my shitty wind reading costs me 1/2 MOA, and spin drift costs me 1/2 MOA, why not try to adress them all?
SPIN DRIFT TOPIC! BRING IT!
Re: Spin drift
"Drift" from a spinning projectile is a fact, but one of the smallest influences in field shooting.
I was on a known distance range that was absolutely still a few years ago. Fog was 1-2 ft thick on the grass, with a very thin mist in the air. The 6.5-284 rifle's zero was confirmed on paper at 100m. We had steel targets at 300m, 600m, 800m and 1000m.
The rifle was shooting great and the groups were all very small for distance (plus/minus 1/2moa). There was no perceptable drift at 300m. There was an inch or so drift at 600m (I wouldn't call it drift if it were not for the ideal shooting and atmospheric conditions). At 800m there was a definite drift of approx. 4" to the right. And at 1000m there was approx. 6" of drift.
We shot some 7.62 and saw approx 50% more drift at each distance, but due to larger groups and the few rounds we shot (due to failing light, dinner and cold beer waiting).
So to answer your question - yes, I allow a program to figure spin drift in it's calculation. But I am focused on reading wind and target speed for horizontal holdoff.
Mike
"Drift" from a spinning projectile is a fact, but one of the smallest influences in field shooting.
I was on a known distance range that was absolutely still a few years ago. Fog was 1-2 ft thick on the grass, with a very thin mist in the air. The 6.5-284 rifle's zero was confirmed on paper at 100m. We had steel targets at 300m, 600m, 800m and 1000m.
The rifle was shooting great and the groups were all very small for distance (plus/minus 1/2moa). There was no perceptable drift at 300m. There was an inch or so drift at 600m (I wouldn't call it drift if it were not for the ideal shooting and atmospheric conditions). At 800m there was a definite drift of approx. 4" to the right. And at 1000m there was approx. 6" of drift.
We shot some 7.62 and saw approx 50% more drift at each distance, but due to larger groups and the few rounds we shot (due to failing light, dinner and cold beer waiting).
So to answer your question - yes, I allow a program to figure spin drift in it's calculation. But I am focused on reading wind and target speed for horizontal holdoff.
Mike
G
Guest
Guest
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRose</div><div class="ubbcode-body">I try to adress every problem... If my shitty form costs me 1/2 MOA, and my shitty wind reading costs me 1/2 MOA, and spin drift costs me 1/2 MOA, why not try to adress them all?
SPIN DRIFT TOPIC! BRING IT! </div></div>
I've been waiting for years on someone we both know,
to saddle up, an shoot this horse,....
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRose</div><div class="ubbcode-body">I try to adress every problem... If my shitty form costs me 1/2 MOA, and my shitty wind reading costs me 1/2 MOA, and spin drift costs me 1/2 MOA, why not try to adress them all?
SPIN DRIFT TOPIC! BRING IT!
to saddle up, an shoot this horse,....
Re: Spin drift
Interestingly,
When we did the finger placement comparison, at 100 yards we couldn't see a difference between using the pad or the joint of the finger at 100, but when we went to 300 yards the difference became apparent. At 300 yards the difference was at least a 1/2", so you have to wonder because changes in groups don't go linear all the time and the shooter's influence forcing that component to "drift' right cannot be easily overlooked. The video illustrates a bit of this, but the groups often posted on here illustrate it even further. I offer those interested to casually look at the "groups" posted on here and see where the majority of the errors are -- as in which direction and how far away.
In the video, using the joint had twice as much deviation right as using the pad... food for thought. If you say you have a 1/2MOA of shooter error, how do you know it stays 1/2MOA and doesn't grow with distance as most normally do. and in which direction is that 1/2MOA of error, so you are in fact compensating for "drift" or shooter error.
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Finally, and I have stated this over and over, not too long ago we had a class of 20 shooters, 19 right handed and 1 left handed including one "known" shooter who has been a student multiple times on the system while a member of the Rangers. Same rifles, ammo, scopes across the board. The "known" shooter used 2.5 Mils of Wind for the 1000 yard target, the average user used about 3.2 mils of wind, with some as much as 3.5 mils of wind. Finally the left handed shooter used 1.5 mils of wind... so empirically what does that say ?
Its as far as I go with SD, and I'm not here to say it doesn't exist, but 12" seems to be a bit extreme if you ask me, then again what do I know. Now, past 1200m, dial away I with you there.
Interestingly,
When we did the finger placement comparison, at 100 yards we couldn't see a difference between using the pad or the joint of the finger at 100, but when we went to 300 yards the difference became apparent. At 300 yards the difference was at least a 1/2", so you have to wonder because changes in groups don't go linear all the time and the shooter's influence forcing that component to "drift' right cannot be easily overlooked. The video illustrates a bit of this, but the groups often posted on here illustrate it even further. I offer those interested to casually look at the "groups" posted on here and see where the majority of the errors are -- as in which direction and how far away.
In the video, using the joint had twice as much deviation right as using the pad... food for thought. If you say you have a 1/2MOA of shooter error, how do you know it stays 1/2MOA and doesn't grow with distance as most normally do. and in which direction is that 1/2MOA of error, so you are in fact compensating for "drift" or shooter error.
<object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/S72ehttwFxw"></param> <param name="wmode" value="transparent"></param> <embed src="http://www.youtube.com/v/S72ehttwFxw" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"> </embed></object>
Finally, and I have stated this over and over, not too long ago we had a class of 20 shooters, 19 right handed and 1 left handed including one "known" shooter who has been a student multiple times on the system while a member of the Rangers. Same rifles, ammo, scopes across the board. The "known" shooter used 2.5 Mils of Wind for the 1000 yard target, the average user used about 3.2 mils of wind, with some as much as 3.5 mils of wind. Finally the left handed shooter used 1.5 mils of wind... so empirically what does that say ?
Its as far as I go with SD, and I'm not here to say it doesn't exist, but 12" seems to be a bit extreme if you ask me, then again what do I know. Now, past 1200m, dial away I with you there.
Re: Spin drift
LL, why argue about the spin drift value? You could ask the good people at Lapua that have radar data for their bullets, available for all...
And if you have .mil friends, I'm sure they can ask for the gyroscopic drift data on all US military loads, all these loads have been radar tested.
LL, why argue about the spin drift value? You could ask the good people at Lapua that have radar data for their bullets, available for all...
And if you have .mil friends, I'm sure they can ask for the gyroscopic drift data on all US military loads, all these loads have been radar tested.
Re: Spin drift
I'm not arguing about anything... but what a rifle does in a fixture and what a rifle does in a shooter's hands has shown to be two completely different things. Not to mention, I doubt they shot it in a wind-less tunnel... do you know if they used a fixture or a shooter also.
I'm not arguing about anything... but what a rifle does in a fixture and what a rifle does in a shooter's hands has shown to be two completely different things. Not to mention, I doubt they shot it in a wind-less tunnel... do you know if they used a fixture or a shooter also.
Re: Spin drift
Good point about a fixture vs shooter, let's look at that.
One big difference between a fixture and a shooter is that the fixture would be leveled, and eliminate any shooter induced cant. The shooter on the other hand, <span style="text-decoration: underline">if working without a level</span>, would cant the rifle somewhat.
To put the spin drift magnitude into perspective, most rounds will see something like 5" to 9" of SD at 1k. Now consider that the bullet will be displaced laterally by about 5" for every 1 degree of rifle cant. Without a level, shooting in the field without a vertical or horizontal reference for your reticle, a typical shooter would be lucky to achieve less than 3 or 5 degrees of cant. The average bias of cant would probably be affected by being left handed vs right handed; hence LL's observation of the left handed shooter using much different wind than the right handed shooter.
My point here is that if you're shooting without a level on your rifle, it's probably not appropriate to try and account for spin drift because the effects of cant will overshadow that (before even considering the wind). However, if you use a properly installed sight level, and your reticle tracks true, then a horizontal drift on the order of 5" to 8" can be seen repeatably in calm conditions. Of course if the wind is a big deal, the spin drift is less significant by comparison, but it's still there.
-Bryan
Good point about a fixture vs shooter, let's look at that.
One big difference between a fixture and a shooter is that the fixture would be leveled, and eliminate any shooter induced cant. The shooter on the other hand, <span style="text-decoration: underline">if working without a level</span>, would cant the rifle somewhat.
To put the spin drift magnitude into perspective, most rounds will see something like 5" to 9" of SD at 1k. Now consider that the bullet will be displaced laterally by about 5" for every 1 degree of rifle cant. Without a level, shooting in the field without a vertical or horizontal reference for your reticle, a typical shooter would be lucky to achieve less than 3 or 5 degrees of cant. The average bias of cant would probably be affected by being left handed vs right handed; hence LL's observation of the left handed shooter using much different wind than the right handed shooter.
My point here is that if you're shooting without a level on your rifle, it's probably not appropriate to try and account for spin drift because the effects of cant will overshadow that (before even considering the wind). However, if you use a properly installed sight level, and your reticle tracks true, then a horizontal drift on the order of 5" to 8" can be seen repeatably in calm conditions. Of course if the wind is a big deal, the spin drift is less significant by comparison, but it's still there.
-Bryan
Re: Spin drift
...I am sure learning a lot in here...
...providing of course that youse guys are not full of crap...
...I am sure learning a lot in here...
...providing of course that youse guys are not full of crap...
Re: Spin drift
I do not factor it in. If I'm within 'spin-drift' distance away from an ELR target, I'm pretty happy with the shot. If I was trying to win bullseye marks in a competition, I probably would give it some thought.
I do not factor it in. If I'm within 'spin-drift' distance away from an ELR target, I'm pretty happy with the shot. If I was trying to win bullseye marks in a competition, I probably would give it some thought.
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body">Good point about a fixture vs shooter, let's look at that.
One big difference between a fixture and a shooter is that the fixture would be leveled, and eliminate any shooter induced cant. The shooter on the other hand, <span style="text-decoration: underline">if working without a level</span>, would cant the rifle somewhat.
To put the spin drift magnitude into perspective, most rounds will see something like 5" to 9" of SD at 1k. Now consider that the bullet will be displaced laterally by about 5" for every 1 degree of rifle cant. Without a level, shooting in the field without a vertical or horizontal reference for your reticle, a typical shooter would be lucky to achieve less than 3 or 5 degrees of cant. The average bias of cant would probably be affected by being left handed vs right handed; hence LL's observation of the left handed shooter using much different wind than the right handed shooter.
My point here is that if you're shooting without a level on your rifle, it's probably not appropriate to try and account for spin drift because the effects of cant will overshadow that (before even considering the wind). However, if you use a properly installed sight level, and your reticle tracks true, then a horizontal drift on the order of 5" to 8" can be seen repeatably in calm conditions. Of course if the wind is a big deal, the spin drift is less significant by comparison, but it's still there.
-Bryan </div></div>
Hey Bryan,
I work with levels for a living (cabinet maker/finish carpenter) and was curious if you can really see 1 degree on your sight level. I have one on my AR30 and think I would be hard pressed to see 1 degree. Just curious.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body">Good point about a fixture vs shooter, let's look at that.
One big difference between a fixture and a shooter is that the fixture would be leveled, and eliminate any shooter induced cant. The shooter on the other hand, <span style="text-decoration: underline">if working without a level</span>, would cant the rifle somewhat.
To put the spin drift magnitude into perspective, most rounds will see something like 5" to 9" of SD at 1k. Now consider that the bullet will be displaced laterally by about 5" for every 1 degree of rifle cant. Without a level, shooting in the field without a vertical or horizontal reference for your reticle, a typical shooter would be lucky to achieve less than 3 or 5 degrees of cant. The average bias of cant would probably be affected by being left handed vs right handed; hence LL's observation of the left handed shooter using much different wind than the right handed shooter.
My point here is that if you're shooting without a level on your rifle, it's probably not appropriate to try and account for spin drift because the effects of cant will overshadow that (before even considering the wind). However, if you use a properly installed sight level, and your reticle tracks true, then a horizontal drift on the order of 5" to 8" can be seen repeatably in calm conditions. Of course if the wind is a big deal, the spin drift is less significant by comparison, but it's still there.
-Bryan </div></div>
Hey Bryan,
I work with levels for a living (cabinet maker/finish carpenter) and was curious if you can really see 1 degree on your sight level. I have one on my AR30 and think I would be hard pressed to see 1 degree. Just curious.
Re: Spin drift
DaveV,
I think 1 degree can be seen in a typical scope level. When I put a level on my angle meter (for measuring the pitch of a roof), it's pretty clear that the level is 'off plumb' when I tilt it by one (metered) degree.
-Bryan
DaveV,
I think 1 degree can be seen in a typical scope level. When I put a level on my angle meter (for measuring the pitch of a roof), it's pretty clear that the level is 'off plumb' when I tilt it by one (metered) degree.
-Bryan
Re: Spin drift
I live in Australia, so any spin drift from a right hand twist barrel is reduced a bit by the influence of the Coriolis effect.
So I wonder why in the U.S. left hand twist barrels are not more popular for long range rifles? Seems like you could reduce the effect of spin drift at no cost.
I live in Australia, so any spin drift from a right hand twist barrel is reduced a bit by the influence of the Coriolis effect.
So I wonder why in the U.S. left hand twist barrels are not more popular for long range rifles? Seems like you could reduce the effect of spin drift at no cost.
Re: Spin drift
Indeed, those effects would offset for left-hand twist barrels in the northern hemisphere, which Bryan mentions in his book.
Indeed, those effects would offset for left-hand twist barrels in the northern hemisphere, which Bryan mentions in his book.
Re: Spin drift
I keep meaning to buy Brian's book. Seems like an interesting read...
I keep meaning to buy Brian's book. Seems like an interesting read...
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRose</div><div class="ubbcode-body">I keep meaning to buy Brian's book. Seems like an interesting read... </div></div>
Yes it is a good read.
By the way, I think the Toyota badge is off the rear quarter panel of a HJ60?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRose</div><div class="ubbcode-body">I keep meaning to buy Brian's book. Seems like an interesting read... </div></div>
Yes it is a good read.
By the way, I think the Toyota badge is off the rear quarter panel of a HJ60?
Re: Spin drift
Actually, emblem's correct.
Actually, emblem's correct.
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body"> Depending on the bullet, twist rate and speed, it will drift to the right anywhere from 2"-5" at 1K. </div></div>
Does twist direction make it go in that direction?
Ex. Left hand twist = drift left 2"-5"...
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body"> Depending on the bullet, twist rate and speed, it will drift to the right anywhere from 2"-5" at 1K. </div></div>
Does twist direction make it go in that direction?
Ex. Left hand twist = drift left 2"-5"...
Re: Spin drift
DaveV, if it's very calm, I factor roughly 1/2moa spin drift starting @ about 600-700 yards. If the wind is blowing over 5mph, I focus more on trying to figure it out than spindrift. Some say it does exist, some say it doesn't. I believe it does based on my experience, but my experience is minor compared to some.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DaveV</div><div class="ubbcode-body">On the new History channel show, one of the shooters said that he calcs for spin drift. Do many of you shooting ELR calc for it or not? </div></div>
DaveV, if it's very calm, I factor roughly 1/2moa spin drift starting @ about 600-700 yards. If the wind is blowing over 5mph, I focus more on trying to figure it out than spindrift. Some say it does exist, some say it doesn't. I believe it does based on my experience, but my experience is minor compared to some.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DaveV</div><div class="ubbcode-body">On the new History channel show, one of the shooters said that he calcs for spin drift. Do many of you shooting ELR calc for it or not? </div></div>
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I'm not arguing about anything... but <span style="font-weight: bold">what a rifle does in a fixture and what a rifle does in a shooter's hands has shown to be two completely different things.</span> Not to mention, <span style="font-weight: bold">I doubt they shot it in a wind-less tunnel... </span>do you know if they used a fixture or a shooter also. </div></div>
LL,
- Regarding drop, wind deflection, gyroscopic drift, etc. the bullet does not know if the rifle was shot from a fixture or from your shoulder. If you can see the relatively small effects or not is another matter, but it is there as is a known quantity.
- The beauty of the radar data + sophisticated firing range where all the variables are measured in sevaral stations downrange is that you can can discern wind effects from the others.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I'm not arguing about anything... but <span style="font-weight: bold">what a rifle does in a fixture and what a rifle does in a shooter's hands has shown to be two completely different things.</span> Not to mention, <span style="font-weight: bold">I doubt they shot it in a wind-less tunnel... </span>do you know if they used a fixture or a shooter also. </div></div>
LL,
- Regarding drop, wind deflection, gyroscopic drift, etc. the bullet does not know if the rifle was shot from a fixture or from your shoulder. If you can see the relatively small effects or not is another matter, but it is there as is a known quantity.
- The beauty of the radar data + sophisticated firing range where all the variables are measured in sevaral stations downrange is that you can can discern wind effects from the others.
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Does twist direction make it go in that direction?</div></div>
Yes. Left-hand twist barrels create drift to the left of the line of the bore.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Does twist direction make it go in that direction?</div></div>
Yes. Left-hand twist barrels create drift to the left of the line of the bore.
Re: Spin drift
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ttam</div><div class="ubbcode-body">Jrose is it the wire mesh grill? </div></div>
Nope.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ttam</div><div class="ubbcode-body">Jrose is it the wire mesh grill? </div></div>
Nope.
Re: Spin drift
Tiro,
The point I am making is, if you look at the difference between moving my finger from the pad to the joint, "I" lose 1/2" of accuracy at 300 yards... that is just changing 1 variable, the point of my finger. Same rifle, video taped so you can see I am not playing favorites. Its pretty clear to see, 1/2" at 300 would end up being a bit more than SD at 1000 with the same rifle.
That is my point and my sole point, you are welcome to dial for SD for any amount based on any data you like, that is your right and privilege, "I" on the other hand, prefer to use my field data, and what I know to be true "Downrange" based not just off my own experience, but my experience observing an "awful" lot of shooters on the line of varying degrees of experience.
I will say, that prior to the last decade it was not taught and I never heard anyone say, that their wind calls only work from the left and not the right...or the other way around. I would think with 30 years of recorded data from say 1980 when Sniper Schools came into their own, someone would have complained, right or wrong, the wind data doesn't work correctly for both 9 or 3 O' Clock, there would have been a noticeable variance. I will say, and agree 12" is significant, and when we are shooting targets, like a Larue, which is 11.75" wide it would have shown to have been an issue long before someone decided it was important to include.
The Human factor cannot be overlooked, regardless of what the radar says... I will also note, that I invite anyone who uses the SD feature of their ballistic calculator to change the "Zero Range" after having noted the 1000 yard SD variance from a 100 yard zero to something like a 300 or even 600 yards zero. I have found it doesn't change the SD answer, which is highly suspect if you ask me, as that means I can't zero it out.
Now, I don't want to sound augmentative, and I am not being so, however if you read Pesja's Modern Ballistics, he very much under plays it, telling you to get a left hand twist barrel and calling it a day. That it is understood that external forces, like Wind, and The Shooter" are far more important variables, to which I fully agree, as do I agree with Brian. I also would say, each barrels twist and muzzle velocity would play a larger part than taking any radar data, because that is only good for that set up and may not translate correctly to what I am using, so why would I dial in ?
More often than not, we have found if the shooter does their part, many of these factors seem to fall further and further from the surface -- which is why I like the way ExBal addresses it, they recommend you shoot and measure a group around 600 yards and that data is then used -- to me, that is the correct way to address the issue, as I have yet to be influenced to the degree I should be if I were go with the published data on the subject -- to which always seems to include the 173gr bullet which isn't really even used anymore. I will say, years ago, I was personally told it was really only a factor at the transonic point, and not well inside the effective range where the bullet was spinning at a stable rate. That information maybe wrong, and contrary to computer models, but it makes sense to me, and how I look at it. I mean when Pesja tells me it is .002" of an inch at 100 yards, if its compounding all the way to 1000 by what factor brings it from .002" to 12" ?
Question my thinking, disregard my opinion on the subject, but I will say this, I will go 1 shot for 1 shot across the cross with anyone, and have no problem putting my thinking to practical application with anyone. So far my track record is pretty good and hanging out there is not a problem, I'm not scared of being proven wrong, or at least enlightened in a practical manner.
Tiro,
The point I am making is, if you look at the difference between moving my finger from the pad to the joint, "I" lose 1/2" of accuracy at 300 yards... that is just changing 1 variable, the point of my finger. Same rifle, video taped so you can see I am not playing favorites. Its pretty clear to see, 1/2" at 300 would end up being a bit more than SD at 1000 with the same rifle.
That is my point and my sole point, you are welcome to dial for SD for any amount based on any data you like, that is your right and privilege, "I" on the other hand, prefer to use my field data, and what I know to be true "Downrange" based not just off my own experience, but my experience observing an "awful" lot of shooters on the line of varying degrees of experience.
I will say, that prior to the last decade it was not taught and I never heard anyone say, that their wind calls only work from the left and not the right...or the other way around. I would think with 30 years of recorded data from say 1980 when Sniper Schools came into their own, someone would have complained, right or wrong, the wind data doesn't work correctly for both 9 or 3 O' Clock, there would have been a noticeable variance. I will say, and agree 12" is significant, and when we are shooting targets, like a Larue, which is 11.75" wide it would have shown to have been an issue long before someone decided it was important to include.
The Human factor cannot be overlooked, regardless of what the radar says... I will also note, that I invite anyone who uses the SD feature of their ballistic calculator to change the "Zero Range" after having noted the 1000 yard SD variance from a 100 yard zero to something like a 300 or even 600 yards zero. I have found it doesn't change the SD answer, which is highly suspect if you ask me, as that means I can't zero it out.
Now, I don't want to sound augmentative, and I am not being so, however if you read Pesja's Modern Ballistics, he very much under plays it, telling you to get a left hand twist barrel and calling it a day. That it is understood that external forces, like Wind, and The Shooter" are far more important variables, to which I fully agree, as do I agree with Brian. I also would say, each barrels twist and muzzle velocity would play a larger part than taking any radar data, because that is only good for that set up and may not translate correctly to what I am using, so why would I dial in ?
More often than not, we have found if the shooter does their part, many of these factors seem to fall further and further from the surface -- which is why I like the way ExBal addresses it, they recommend you shoot and measure a group around 600 yards and that data is then used -- to me, that is the correct way to address the issue, as I have yet to be influenced to the degree I should be if I were go with the published data on the subject -- to which always seems to include the 173gr bullet which isn't really even used anymore. I will say, years ago, I was personally told it was really only a factor at the transonic point, and not well inside the effective range where the bullet was spinning at a stable rate. That information maybe wrong, and contrary to computer models, but it makes sense to me, and how I look at it. I mean when Pesja tells me it is .002" of an inch at 100 yards, if its compounding all the way to 1000 by what factor brings it from .002" to 12" ?
Question my thinking, disregard my opinion on the subject, but I will say this, I will go 1 shot for 1 shot across the cross with anyone, and have no problem putting my thinking to practical application with anyone. So far my track record is pretty good and hanging out there is not a problem, I'm not scared of being proven wrong, or at least enlightened in a practical manner.
Re: Spin drift
With the direction these spin drift topics seem to head, I thought fitting to share Lindy's quote...
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Four stages of acceptance:
i) this is worthless nonsense;
ii) this is an interesting, but perverse, point of view;
iii) this is true, but quite unimportant;
iv) I always said so.
</div></div>
With the direction these spin drift topics seem to head, I thought fitting to share Lindy's quote...
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Four stages of acceptance:
i) this is worthless nonsense;
ii) this is an interesting, but perverse, point of view;
iii) this is true, but quite unimportant;
iv) I always said so.
</div></div>
Re: Spin drift
My take away so far is that nobody claims SD doesn't exist. The arguments come down to:
1) Is it an issue throughout the bullet flight path that should be accounted for?
2) Past 1000 yards, is it an effect which can even be verified with a first round hit because of the myriad factors of internal and external ballistic variables?
3) Does a corrected follow up shot make it a mute point?
Did I miss any?
My take away so far is that nobody claims SD doesn't exist. The arguments come down to:
1) Is it an issue throughout the bullet flight path that should be accounted for?
2) Past 1000 yards, is it an effect which can even be verified with a first round hit because of the myriad factors of internal and external ballistic variables?
3) Does a corrected follow up shot make it a mute point?
Did I miss any?
Re: Spin drift
Dave,
Perhaps another way to approach the question is to ask;
Does a clear understanding of the phenomena of spin-drift make one a good shot? (No)
Do current practical compensatory measures, developed wittingly or not, provide an adequate strategy for addressing the effect at increasingly extended ranges? (No)
Is an accomplished marksman able to benefit from a conceptual grasp of the physics involved? (In my opinion, yes... provided he is targeting at ranges where "fudge" factors lose utility)
P.S.; There is an operational targeting system that takes the "art" out of wind-drift calculation. This brings spin-drift to the surface. I am certain that I am not the only person here who knows about it.
Dave,
Perhaps another way to approach the question is to ask;
Does a clear understanding of the phenomena of spin-drift make one a good shot? (No)
Do current practical compensatory measures, developed wittingly or not, provide an adequate strategy for addressing the effect at increasingly extended ranges? (No)
Is an accomplished marksman able to benefit from a conceptual grasp of the physics involved? (In my opinion, yes... provided he is targeting at ranges where "fudge" factors lose utility)
P.S.; There is an operational targeting system that takes the "art" out of wind-drift calculation. This brings spin-drift to the surface. I am certain that I am not the only person here who knows about it.
Re: Spin drift
Projectiles from any and all rifled weapons (rifles, pistols, mortars, artillery) will drift due to rifling spin. Faster twist will induce more drift. This is a common phenomena all artillery and mortarmen are trained to compensate for.
It is largely unknown by riflemen because the majority will never shoot at extended ranges.
Anyone can pick up a copy of <span style="font-weight: bold">Understanding Firearm Ballistics</span> by Robert A. Rinker from one of the big mass/mall bookstores. Chapter 9 of the 2009 6th edition goes into 8-pages of boring detail about spin-gyroscopic drift.
Projectiles from any and all rifled weapons (rifles, pistols, mortars, artillery) will drift due to rifling spin. Faster twist will induce more drift. This is a common phenomena all artillery and mortarmen are trained to compensate for.
It is largely unknown by riflemen because the majority will never shoot at extended ranges.
Anyone can pick up a copy of <span style="font-weight: bold">Understanding Firearm Ballistics</span> by Robert A. Rinker from one of the big mass/mall bookstores. Chapter 9 of the 2009 6th edition goes into 8-pages of boring detail about spin-gyroscopic drift.
Re: Spin drift
All,
I'm not sayind that you should/must dial the gyroscopic drift at less than 1000 yds, as there are more FAR more important effects (drop, the ever changing wind, environmental conditions, vertical angle) that tend to blurr this effect at long range.
As LL mentioned, even an individual shooter may cant the rifle a tiny amount, or jerk the triger, etc. consistently, further to complicate things. Or perhaps the scope has some manufacturing or mounting deffect that cants the vertical reticle movement a little bit and shows at long range.
But in an ideal setting, without these errors and with no wind (or aligned with it, a 30º angle has a 50% effect compared to a 3:00 wind, a 15º wind has 26% the effect) the typical +/- 1-2 mph error in wind estimation is minimized, and a 1.0 MOA effect is certainly significant. And at very long ranges (>1200 yds) the effect is very significant (again, ask Lapua for their 338 LM data).
Also arguing about SD and its value (about 1.0 MOA at 1000 yds, for modern sniper 308 loads) is kind of silly. It is a well known value for all military loads thanks to extensive tests, but it is difficult or even impossible to ascern with any degree of precision for any shooter. If you want to know the number, ask the few makers that know it (Lapua has it available for everyone, Sierra -whose bullets are used in all US sniper loads- has it as kind of restricted information) or for the .mil tables.
Using a left hand barrels twist does nothing for SD, just inverses the direction of the effect. With a LH twist the Coriolis effect would tend to cancel with the SD in the northern hemisphere, but the SD effect is much larger, and the Coriolis effect varies a lot from the Equator to the pole... why bother?
LL, I don't know about the program that you are using, but the SD at 300 is veeery small, and for 1000 yds you have a correction that is veeery close to the one with a 100 yds zero. This is because it is an effect that more or less varies with the 3rd power of the range. Most (all?) programs just estimate (NOT calculate) the SD of most loads based on similar bullets that have known data.
All,
I'm not sayind that you should/must dial the gyroscopic drift at less than 1000 yds, as there are more FAR more important effects (drop, the ever changing wind, environmental conditions, vertical angle) that tend to blurr this effect at long range.
As LL mentioned, even an individual shooter may cant the rifle a tiny amount, or jerk the triger, etc. consistently, further to complicate things. Or perhaps the scope has some manufacturing or mounting deffect that cants the vertical reticle movement a little bit and shows at long range.
But in an ideal setting, without these errors and with no wind (or aligned with it, a 30º angle has a 50% effect compared to a 3:00 wind, a 15º wind has 26% the effect) the typical +/- 1-2 mph error in wind estimation is minimized, and a 1.0 MOA effect is certainly significant. And at very long ranges (>1200 yds) the effect is very significant (again, ask Lapua for their 338 LM data).
Also arguing about SD and its value (about 1.0 MOA at 1000 yds, for modern sniper 308 loads) is kind of silly. It is a well known value for all military loads thanks to extensive tests, but it is difficult or even impossible to ascern with any degree of precision for any shooter. If you want to know the number, ask the few makers that know it (Lapua has it available for everyone, Sierra -whose bullets are used in all US sniper loads- has it as kind of restricted information) or for the .mil tables.
Using a left hand barrels twist does nothing for SD, just inverses the direction of the effect. With a LH twist the Coriolis effect would tend to cancel with the SD in the northern hemisphere, but the SD effect is much larger, and the Coriolis effect varies a lot from the Equator to the pole... why bother?
LL, I don't know about the program that you are using, but the SD at 300 is veeery small, and for 1000 yds you have a correction that is veeery close to the one with a 100 yds zero. This is because it is an effect that more or less varies with the 3rd power of the range. Most (all?) programs just estimate (NOT calculate) the SD of most loads based on similar bullets that have known data.
Re: Spin drift
Dave
For me:
Field Practical Rifle at 1000 yards or closer, no - not really. Heavy Rifle (50 Cal.) at LR - ELR ranges, yes. No arguements here - to each their own - live & let live... and all that good stuff ;O) I dont put much stock in what everyone else does or says, or the popular consensus anyway.
Aug ><>
Dave
For me:
Field Practical Rifle at 1000 yards or closer, no - not really. Heavy Rifle (50 Cal.) at LR - ELR ranges, yes. No arguements here - to each their own - live & let live... and all that good stuff ;O) I dont put much stock in what everyone else does or says, or the popular consensus anyway.
Aug ><>
Re: Spin drift
I'd have to put way more rounds down range to tell, but I cant tell.
I'd have to put way more rounds down range to tell, but I cant tell.
Re: Spin drift
FWIW, today we shot @ 705 yards. I shot first @ 100 to verify the zero and then to 705. First 5 shot group was about 3.5" right with a 3-5 mph wind from 12 o'clock. I corrected .5 moa left and second 5 shot group was on bullseye.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DaveV</div><div class="ubbcode-body">Again, lest my OP spin drift itself, my question is to those who "do" or "don't" calc for it. Not just theory, but practice. Thanks all. </div></div>
FWIW, today we shot @ 705 yards. I shot first @ 100 to verify the zero and then to 705. First 5 shot group was about 3.5" right with a 3-5 mph wind from 12 o'clock. I corrected .5 moa left and second 5 shot group was on bullseye.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DaveV</div><div class="ubbcode-body">Again, lest my OP spin drift itself, my question is to those who "do" or "don't" calc for it. Not just theory, but practice. Thanks all. </div></div>
