Spin drift
- Thread starter sierra22
- Start date
I agree with JB, I shoot a lot from 400 to 800yds and have not noticed any spin drift problem. I have yet to have many days where its calm enough to tell.
I shoot a 6XC, 260 and 6.5x55 and all of these guns have the 1-8 twist. I have had a few days where the gun may have had a tendency to group to the right at 700 and 800yds but not enough to say it was anything to worry about.
I don't think this is something you need to worry about until you get wayyyyyyy..... out there. Most of the time enviromental factors overshadow the spindrift.
I shoot a 6XC, 260 and 6.5x55 and all of these guns have the 1-8 twist. I have had a few days where the gun may have had a tendency to group to the right at 700 and 800yds but not enough to say it was anything to worry about.
I don't think this is something you need to worry about until you get wayyyyyyy..... out there. Most of the time enviromental factors overshadow the spindrift.
Sierra
Most ballisticians agree that there is a small crossrange deflection of a bullet due to it's right or left spin. Most also agree that it is very small but cannot be quantified because of the dynamic properties of bullets that are not known and cannot be measured because testing facilities are prohibitively costly for the average bullet manufacturer. If you can indeed identify it and seperate it from all the other environmental factors that you have to deal with at long range, you are a far better LR shooter than I am. It's only my guess but I think the deflections you are seeing are the result of something other than bullet rotation. Wind, of course, is the most likely culprit but things such as canting the rifle or a scope not centered over the bore could also account for it. JMHO
Ray
Most ballisticians agree that there is a small crossrange deflection of a bullet due to it's right or left spin. Most also agree that it is very small but cannot be quantified because of the dynamic properties of bullets that are not known and cannot be measured because testing facilities are prohibitively costly for the average bullet manufacturer. If you can indeed identify it and seperate it from all the other environmental factors that you have to deal with at long range, you are a far better LR shooter than I am. It's only my guess but I think the deflections you are seeing are the result of something other than bullet rotation. Wind, of course, is the most likely culprit but things such as canting the rifle or a scope not centered over the bore could also account for it. JMHO
Ray
I shoot a 260 with 139's in an 8 twist and I have to dial left windage for a good 'no wind zero'.
But there are a few instances where the amount needed is more or less.
For example- If the sun is at my 4 oclock, then I don't have to dial left windage until 800+ yds.
800- requires .5 moa left
900- same.
1k same.
If sun is at 8 oclock, then I have to dial .25-.5 moa left as early as 600 yds and then go to .75 for 800-1k. This also depends on how high or low the sun is.
If it's overcast, with sun at 8-9, then I do not have to dial left windage at 600, but still have to at 800-1k.
The range faces WNW.
Night time shooting to 1k using one spotlight, wether at 3-6 or 9 oclock, lighting the target from the 900 yard line, is something everyone should do.
But there are a few instances where the amount needed is more or less.
For example- If the sun is at my 4 oclock, then I don't have to dial left windage until 800+ yds.
800- requires .5 moa left
900- same.
1k same.
If sun is at 8 oclock, then I have to dial .25-.5 moa left as early as 600 yds and then go to .75 for 800-1k. This also depends on how high or low the sun is.
If it's overcast, with sun at 8-9, then I do not have to dial left windage at 600, but still have to at 800-1k.
The range faces WNW.
Night time shooting to 1k using one spotlight, wether at 3-6 or 9 oclock, lighting the target from the 900 yard line, is something everyone should do.
BHarvey said:
B
I'm not saying that "spin deflection" does not exist but your post raises some big questions in my mind.
What would the position of the sun or lighting have to do with it? Wouldn't that indicate that the deflection is due to displacement of the target image due to light, such as happens with mirage or clouds?
When you refer to "a good no wind zero" what is your base reference? In other words, .5 MOA left from what?
Ray
.5 moa left from my 100 yd zero.
Light condition has a big effect on POI. Not only moving your POI up/down but left/right as well.
Try this sometime and post results. Get zerod at 100, then wait for night fall. Now position a flashlight at 9 oclock level with the target, note POI.
Then try 3 Oclock and not POI.
Then try 12 and 6 oclock and note POI.
The change in direction of the light will change your POI.
As far as a 'good no wind zero', when you have access to a 1k range at anytime of the day, you will be able to shoot with very little and sometimes NO conditions.
It is very common for almost all calibers to exhibit a change in your 'windage zero' when shooting from 100-1k.
Most 12 twist 308's with 175's will exhibit a need of .5 moa of left wind. A 10 twist 308 with 175's at the same speed will need 1.25-1.5 moa left windage.
At night with 5 shooters on the line and ALL hitting the SAME amount right of POA says something. We all shot 10 shots at the same time. With the massive difference in wind drift between the cartridges present, and considering we all hit the same amount right of POA tells me that the conditions were calm.
All three 308's were 12 twist, the 260 and 6.5-06 were 8 twist's.
The 308 with the 10 twist is owned by the man who owns the range and has 30 years experience LR shooting. The left windage data came from him.
Light condition has a big effect on POI. Not only moving your POI up/down but left/right as well.
Try this sometime and post results. Get zerod at 100, then wait for night fall. Now position a flashlight at 9 oclock level with the target, note POI.
Then try 3 Oclock and not POI.
Then try 12 and 6 oclock and note POI.
The change in direction of the light will change your POI.
As far as a 'good no wind zero', when you have access to a 1k range at anytime of the day, you will be able to shoot with very little and sometimes NO conditions.
It is very common for almost all calibers to exhibit a change in your 'windage zero' when shooting from 100-1k.
Most 12 twist 308's with 175's will exhibit a need of .5 moa of left wind. A 10 twist 308 with 175's at the same speed will need 1.25-1.5 moa left windage.
At night with 5 shooters on the line and ALL hitting the SAME amount right of POA says something. We all shot 10 shots at the same time. With the massive difference in wind drift between the cartridges present, and considering we all hit the same amount right of POA tells me that the conditions were calm.
All three 308's were 12 twist, the 260 and 6.5-06 were 8 twist's.
The 308 with the 10 twist is owned by the man who owns the range and has 30 years experience LR shooting. The left windage data came from him.
QUOTE "Light condition has a big effect on POI. Not only moving your POI up/down but left/right as well... The change in direction of the light will change your POI." QUOTE
That was exactly my point. I must have misunderstood your post because I thought you were saying that the light source and direction was changing the amount of spin deflection.
My other point was that a .5 MOA deflection at 1000 yards would probably not be noticeable at 100 yards.
Ray
That was exactly my point. I must have misunderstood your post because I thought you were saying that the light source and direction was changing the amount of spin deflection.
My other point was that a .5 MOA deflection at 1000 yards would probably not be noticeable at 100 yards.
Ray
"Light condition has a big effect on POI. Not only moving your POI up/down but left/right as well... The change in direction of the light will change your POI." QUOTE
That was exactly my point. I must have misunderstood your post because I thought you were saying that the light source and direction was changing the amount of spin deflection.
Light direction adds/subtracts to/from the amount of correction needed based on a 100 yard zero. But the deflection is still there from 800-1k no matter what direction or light condition encountered.
My other point was that a .5 MOA deflection at 1000 yards would probably not be noticeable at 100 yards.
If you zero at 1k and then come down on elevation to shoot at 100, you will notice the difference. The same difference encountered when going from 100 to 1k.
That was exactly my point. I must have misunderstood your post because I thought you were saying that the light source and direction was changing the amount of spin deflection.
Light direction adds/subtracts to/from the amount of correction needed based on a 100 yard zero. But the deflection is still there from 800-1k no matter what direction or light condition encountered.
My other point was that a .5 MOA deflection at 1000 yards would probably not be noticeable at 100 yards.
If you zero at 1k and then come down on elevation to shoot at 100, you will notice the difference. The same difference encountered when going from 100 to 1k.
bharvey
Load development at long range has always been one of the dilemmas faced by shooters. Not having access to a 1000 yard range,except during matches) I have never been able to test under the near perfect conditions that you've described. I'd like to ask you a few questions so I have a better idea of what to look for if I ever get the opportunity.
5-shot groups? 10-shot groups?
How many groups do you shoot from each rifle in one session?
How big are the groups?
Are all groups from one rifle of the same approximate size?
Are the groups round?
Flyers?
Do you chronograph while shooting? Is there any correlation between ES, SD, and group size or shape?
Any help would be appreciated. Thanks
Ray
Load development at long range has always been one of the dilemmas faced by shooters. Not having access to a 1000 yard range,except during matches) I have never been able to test under the near perfect conditions that you've described. I'd like to ask you a few questions so I have a better idea of what to look for if I ever get the opportunity.
5-shot groups? 10-shot groups?
How many groups do you shoot from each rifle in one session?
How big are the groups?
Are all groups from one rifle of the same approximate size?
Are the groups round?
Flyers?
Do you chronograph while shooting? Is there any correlation between ES, SD, and group size or shape?
Any help would be appreciated. Thanks
Ray
bharvey
Load development at long range has always been one of the dilemmas faced by shooters. Not having access to a 1000 yard range,except during matches) I have never been able to test under the near perfect conditions that you've described. I'd like to ask you a few questions so I have a better idea of what to look for if I ever get the opportunity.
5-shot groups? 10-shot groups?As many 5 shot groups as I could get down range before conditions started to play a part, wether it was wind or mirage, or both. This was usually done from 0530-0700.
How many groups do you shoot from each rifle in one session?I could most of the time get 5-5shot groups in as I was trying not to heat up the barrel too much.
How big are the groups?In the usual condition in the early morning, with a tuned load, all groups were under moa with the majority being between .5 and .75 moa.
Are all groups from one rifle of the same approximate size?Yes
Are the groups round?I'd say it was more 50/50 with group shape, either round or mostly windage spread.
Flyers?With good conditions flyers were very rare. Once you started noticing mirage in your scope picture then it starts getting tricky and stray shots were more common.
Do you chronograph while shooting? Is there any correlation between ES, SD, and group size or shape?Yes, using a 35 with a 4' rail. If I was toward the top side of the node, the ES seemed more critical. If I was in the middle of a node, I would see an ES as high as 40 fps and the group still displayed close to .5 moa of vertical. In the middle of the node, my ES was pretty constant at around 30 fps but the groups were nice and round.
One very calm night I put 10 rounds inside 3" and it was the most beautifully shaped round group I have ever shot. Fun stuff. Wish I could do it in poor shooting conditions. When it gets bad I am glad to hold 2 moa.
Load development at long range has always been one of the dilemmas faced by shooters. Not having access to a 1000 yard range,except during matches) I have never been able to test under the near perfect conditions that you've described. I'd like to ask you a few questions so I have a better idea of what to look for if I ever get the opportunity.
5-shot groups? 10-shot groups?As many 5 shot groups as I could get down range before conditions started to play a part, wether it was wind or mirage, or both. This was usually done from 0530-0700.
How many groups do you shoot from each rifle in one session?I could most of the time get 5-5shot groups in as I was trying not to heat up the barrel too much.
How big are the groups?In the usual condition in the early morning, with a tuned load, all groups were under moa with the majority being between .5 and .75 moa.
Are all groups from one rifle of the same approximate size?Yes
Are the groups round?I'd say it was more 50/50 with group shape, either round or mostly windage spread.
Flyers?With good conditions flyers were very rare. Once you started noticing mirage in your scope picture then it starts getting tricky and stray shots were more common.
Do you chronograph while shooting? Is there any correlation between ES, SD, and group size or shape?Yes, using a 35 with a 4' rail. If I was toward the top side of the node, the ES seemed more critical. If I was in the middle of a node, I would see an ES as high as 40 fps and the group still displayed close to .5 moa of vertical. In the middle of the node, my ES was pretty constant at around 30 fps but the groups were nice and round.
One very calm night I put 10 rounds inside 3" and it was the most beautifully shaped round group I have ever shot. Fun stuff. Wish I could do it in poor shooting conditions. When it gets bad I am glad to hold 2 moa.
I'm not that good a shot, but thx 
My group size? Dunno really. About 2-3" @ 300m. I'm shooting mostly singles at small silhuettes beyond that. As some will derive from this and the below text, I'm not a competition shooter.
The "spin drift",as I have named it for lack of other fitting names)was dicovered during last shooting session as a deviation where I and my spotter called my shots. By clicking for spin, the deviation disappeared. Mirage was moving R-L, so impact should have moved left with distance, not right. As stated, this might be a fluke and I was looking for your experiences.
Spin drift is as previously stated a small effect; measured in inches//centimeters, drift is by far smaller than group.
In my opinion however, accuracy is cumulative and spin drift is corrected mechanically/without thought corresponding to distance.
This would be a lot easier with an illustration, but picture this: Take an ordinary piece of paper. This is your target at whatever distance. Take a second piece of paper, same size, and cut a circle as large as possible. This circle is your group size average.
If cut correctly, your group,circle) just barely fits inside your target,square). Wherever your bullets may land, they will all still hit your target).
Now move you group 4" left. As you see now your bullets may or may not hit your target. Every shot might land outside the target or every shot might land on the target.
Those 4" or 2 clicks@600m in my case might seem insignificant compared to group size, but they can wreak havoc on your hit probability.
As I sidenote I can say that with my 6x45,my most accurate rifle) you can really see the group shifting distinctly to the right as distance increases. This was the first rifle I ever saw this phenomena with, and boy did it cause a few grey hairs before I figured the reason.
Hopefully the discussion will continue with curiousity and keen interest. I don't have a NASA lab to prove anything, I'm just venting some of my thoughts in hopes of playing internet-ball with the amassed experience of this forum. Looking forward to your replies.:comp:
My group size? Dunno really. About 2-3" @ 300m. I'm shooting mostly singles at small silhuettes beyond that. As some will derive from this and the below text, I'm not a competition shooter.
The "spin drift",as I have named it for lack of other fitting names)was dicovered during last shooting session as a deviation where I and my spotter called my shots. By clicking for spin, the deviation disappeared. Mirage was moving R-L, so impact should have moved left with distance, not right. As stated, this might be a fluke and I was looking for your experiences.
Spin drift is as previously stated a small effect; measured in inches//centimeters, drift is by far smaller than group.
In my opinion however, accuracy is cumulative and spin drift is corrected mechanically/without thought corresponding to distance.
This would be a lot easier with an illustration, but picture this: Take an ordinary piece of paper. This is your target at whatever distance. Take a second piece of paper, same size, and cut a circle as large as possible. This circle is your group size average.
If cut correctly, your group,circle) just barely fits inside your target,square). Wherever your bullets may land, they will all still hit your target).
Now move you group 4" left. As you see now your bullets may or may not hit your target. Every shot might land outside the target or every shot might land on the target.
Those 4" or 2 clicks@600m in my case might seem insignificant compared to group size, but they can wreak havoc on your hit probability.
As I sidenote I can say that with my 6x45,my most accurate rifle) you can really see the group shifting distinctly to the right as distance increases. This was the first rifle I ever saw this phenomena with, and boy did it cause a few grey hairs before I figured the reason.
Hopefully the discussion will continue with curiousity and keen interest. I don't have a NASA lab to prove anything, I'm just venting some of my thoughts in hopes of playing internet-ball with the amassed experience of this forum. Looking forward to your replies.:comp:
Sierra22,
Reading your last post I don't know if your text is something you wrote or your quoting an article. I still say that "Spindrift" is so minor that it is not really noticalbe under most conditions.
I live in South Dakota and the wind blows all the time. I can count on one hand the number of days that I may get an hour or two of what I would call no wind conditions. As B.Harvey stated a .5 moa correction at 1000yds is insignificant under real world conditions. First off most of us can't hold .5moa at 1000yds under field conditions and the spindrift thing just sort of gets swallowed up in all the other things we have to worry about when shooting to 1000yds. If you have near no wind conditions to shoot in then it will usually only affect you on out around the 800yd+ mark. Anyway this has been my experience in the couple of times I have shot under near perfect conditions. The problem is where I live I don't think I ever have a real "NO" wind condition.
Reading your last post I don't know if your text is something you wrote or your quoting an article. I still say that "Spindrift" is so minor that it is not really noticalbe under most conditions.
I live in South Dakota and the wind blows all the time. I can count on one hand the number of days that I may get an hour or two of what I would call no wind conditions. As B.Harvey stated a .5 moa correction at 1000yds is insignificant under real world conditions. First off most of us can't hold .5moa at 1000yds under field conditions and the spindrift thing just sort of gets swallowed up in all the other things we have to worry about when shooting to 1000yds. If you have near no wind conditions to shoot in then it will usually only affect you on out around the 800yd+ mark. Anyway this has been my experience in the couple of times I have shot under near perfect conditions. The problem is where I live I don't think I ever have a real "NO" wind condition.
I wrote it.
Guess we're talking/writing slightly past each other.
I'm not disputing that spin drift is small.
I'm not claiming that I my hold is inside the spin drift deviation.
I do however without thought correct for spin drift, no matter what the wind conditions, because I was taught to do so and am hitting targets at present. Would not correcting for spin cause me to miss? Dunno, I'm drilled to do it this way and just do it. The whole correcting-for-spin-drift-thing is not an issue for me here.
My case/problem: At last shooting session I had an unexpected deviation. Mirage said impact left, target said impact right. And I was wondering if this COULD be caused by spin drift.
I am at present at a loss as to what caused the deviation between call/impact. Normally I would just say "shooter", but the target impact responded perfectly to two left clicks and that is what's eating me: Why right impact when it should be left?
Spin drift COULD be an explanation, but the ranges/correction does not correspond to my data tables so I have nothing to support this assumption. As the barrel/bullet/twist is new to me, and I have very little experience shooting different calibers, I was asking if anyone out there has noticed spin drift or different drift between calibers.
Guess not. Hopefully I explained myself more clearly now, English is not my native tongue.
Guess we're talking/writing slightly past each other.
I'm not disputing that spin drift is small.
I'm not claiming that I my hold is inside the spin drift deviation.
I do however without thought correct for spin drift, no matter what the wind conditions, because I was taught to do so and am hitting targets at present. Would not correcting for spin cause me to miss? Dunno, I'm drilled to do it this way and just do it. The whole correcting-for-spin-drift-thing is not an issue for me here.
My case/problem: At last shooting session I had an unexpected deviation. Mirage said impact left, target said impact right. And I was wondering if this COULD be caused by spin drift.
I am at present at a loss as to what caused the deviation between call/impact. Normally I would just say "shooter", but the target impact responded perfectly to two left clicks and that is what's eating me: Why right impact when it should be left?
Spin drift COULD be an explanation, but the ranges/correction does not correspond to my data tables so I have nothing to support this assumption. As the barrel/bullet/twist is new to me, and I have very little experience shooting different calibers, I was asking if anyone out there has noticed spin drift or different drift between calibers.
Guess not. Hopefully I explained myself more clearly now, English is not my native tongue.
Mirage is usually, but not always, a good indicator of wind direction and velocity. I've seen plenty of cases where I had to correct in the same direction as the mirage was running. I can only guess that in those cases the displacement of the target image in the direction of the mirage was greater than the deflection of the bullet in the wind. But since I've also seen cases where the necessary correction was double what the mirage read, I know that the mirage doesn't always tell the full story of wind conditions.
OTOH, mirage is really good at telling you when the condition has changed. So, once you have a zero for a condition, you can correct right or left as that condition picks up or lets off with a lot of confidence. That is, until it changes direction altogether....
I'm not disagreeing with the possible need to correct for spin drift, just noting another possible cause for the phenomenon that you witnessed that one day.
BTW, how do you like your 6x45? I've been thinking of building one myself, but I felt I should hold out for a PPC instead,I'm holding out for one of the Sako repeaters set up for PPCs).
robert
OTOH, mirage is really good at telling you when the condition has changed. So, once you have a zero for a condition, you can correct right or left as that condition picks up or lets off with a lot of confidence. That is, until it changes direction altogether....
I'm not disagreeing with the possible need to correct for spin drift, just noting another possible cause for the phenomenon that you witnessed that one day.
BTW, how do you like your 6x45? I've been thinking of building one myself, but I felt I should hold out for a PPC instead,I'm holding out for one of the Sako repeaters set up for PPCs).
robert
rstreich, thank you very much! Not all that much mirage over here, so I have limited experience shooting in it.
I love my 6x45 or 6mm-223. Cheap and easy to reload. Have shot 20 something deer with it now,roe) but be careful with shot placement. A lung shot gives a runner, but breaking bones puts them down. I'm using n130 and N133 powders and 80-90gr bullet weights @ about 820-830 m/sec.
Cartridge choice was dictated by the small Vixen action, would have a bigger cartridge if it had been a bigger action.
I love my 6x45 or 6mm-223. Cheap and easy to reload. Have shot 20 something deer with it now,roe) but be careful with shot placement. A lung shot gives a runner, but breaking bones puts them down. I'm using n130 and N133 powders and 80-90gr bullet weights @ about 820-830 m/sec.
Cartridge choice was dictated by the small Vixen action, would have a bigger cartridge if it had been a bigger action.
Sierra - I don't mean to hijack your thread about spin drift but I was afraid that if I started a new thread I would lose the attention of the guys who have been posting on this one. But I'll move mine if you want me to.
Those of you who have read some of my other posts know that I usually avoid "deep" discussions about shooting and tend to approach it from a practical point. But this is a really interesting thread and has got me going, so bear with me.
My view is that all ballistics are governed by the laws of physics and that you can't break the laws, or bend them, even if you tried. Whenever the actual results on paper seem to contradict the laws there has to be a reason and I believe that reason is either environmental or the shooter himself. That's why I asked Bharvey those questions, because I've never had the chance to do serious long range load development under ideal conditions and I was curious to what extent his real-world results conflicted with the laws, or with all those urban myths that we see on the internet all the time.
Round groups - under ideal conditions long range groups should NOT be round, according to the laws. There should always be a bigger vertical element due to differences in velocity. But BH says his are round or tending toward horizontal. Does this mean that there really is no "perfect" or "ideal" condition even though it appears to be so? My guess is Yes. There is always SOMETHING going on in all that air between the muzzle and target.
Group size - according to the laws, group size should be linear to the distance. But anyone who has done any shooting beyond 100 yards knows this is not the case so the difference must be, again, the shooter or the environnment. I forgot to ask BH what his group size was at 100 yards, but assuming it is, say, 1/4 MOA, his 1000 yard groups should be 1/4 MOA. But they were actually between .5 and .75 MOA,. I've always believed that a shooter should strive to develop a load that shot little dots at 100 yards because the groups would only get bigger at 1000, and not by a factor of 10 as some would believe. On the other hand if BH is getting only 1/2 MOA at 100 that kinda shoots my theory to hell. So I have to ask BH, what are your 100 yard group sizes with that rifle?
But BH's most interesting comment was in regards ES, SD and vertical. I have never been a believer in the theory that low ES automatically meant less vertical. My own experience, and others I shoot with, has been that some good loads shot very good at 1000 yards in spite of high ES. Maybe he's onto something with his comments about nodes and we should be paying more attention to them.
I realize a few results by one shooter don't mean much in the big picture but I found them interesting.
Now, how many of you think that different diameter and weight bullets of the same BC at the same velocity all show the same wind deflection? I do.
Ray
Those of you who have read some of my other posts know that I usually avoid "deep" discussions about shooting and tend to approach it from a practical point. But this is a really interesting thread and has got me going, so bear with me.
My view is that all ballistics are governed by the laws of physics and that you can't break the laws, or bend them, even if you tried. Whenever the actual results on paper seem to contradict the laws there has to be a reason and I believe that reason is either environmental or the shooter himself. That's why I asked Bharvey those questions, because I've never had the chance to do serious long range load development under ideal conditions and I was curious to what extent his real-world results conflicted with the laws, or with all those urban myths that we see on the internet all the time.
Round groups - under ideal conditions long range groups should NOT be round, according to the laws. There should always be a bigger vertical element due to differences in velocity. But BH says his are round or tending toward horizontal. Does this mean that there really is no "perfect" or "ideal" condition even though it appears to be so? My guess is Yes. There is always SOMETHING going on in all that air between the muzzle and target.
Group size - according to the laws, group size should be linear to the distance. But anyone who has done any shooting beyond 100 yards knows this is not the case so the difference must be, again, the shooter or the environnment. I forgot to ask BH what his group size was at 100 yards, but assuming it is, say, 1/4 MOA, his 1000 yard groups should be 1/4 MOA. But they were actually between .5 and .75 MOA,. I've always believed that a shooter should strive to develop a load that shot little dots at 100 yards because the groups would only get bigger at 1000, and not by a factor of 10 as some would believe. On the other hand if BH is getting only 1/2 MOA at 100 that kinda shoots my theory to hell. So I have to ask BH, what are your 100 yard group sizes with that rifle?
But BH's most interesting comment was in regards ES, SD and vertical. I have never been a believer in the theory that low ES automatically meant less vertical. My own experience, and others I shoot with, has been that some good loads shot very good at 1000 yards in spite of high ES. Maybe he's onto something with his comments about nodes and we should be paying more attention to them.
I realize a few results by one shooter don't mean much in the big picture but I found them interesting.
Now, how many of you think that different diameter and weight bullets of the same BC at the same velocity all show the same wind deflection? I do.
Ray
Forum Boss
Administrator
Ray wrote: Group size - according to the laws, group size should be linear to the distance. But anyone who has done any shooting beyond 100 yards knows this is not the case so the difference must be, again, the shooter or the environnment. I forgot to ask BH what his group size was at 100 yards, but assuming it is, say, 1/4 MOA, his 100 yard groups should be 1/4 MOA. But they were actually between .5 and .75 MOA,. I've always believed that a shooter should strive to develop a load that shot little dots at 100 yards because the groups would only get bigger at 1000, and not by a factor of 10 as some would believe.
- - -
One thing to add to Ray's point is that yes, absent wind effects, horizontal group size should increase directly in direct proportion to distance. That is, a group at 400 yards should be 4x the size of the 100-yard group.
However, WIND--even a tiny amount of wind--changes all that because the effect of,90-deg) wind deflection, roughly speaking, goes up with the SQUARE of the distance.,If this seems counter-intuitive, you can plot the drift using a series of right triangles and see how it works). Here, for example is the drift from a 105gr Scenar in a 10mph 90-degree crosswind.
Actual Deflection from 10 mph X-wind
100 yards: 0.58"
200 yards: 2.33" ,Rule of Square result: 4 x .58" = 2.32")
400 yards: 9.63" ,Rule of Square result: 16 x .58" = 9.28")
600 yards: 23.21",Rule of Square result: 36 x .58" = 20.88")
This simply means as you move further out, the effect of the wind goes up dramatically, making it much more difficult to shoot those tiny groups.
- - -
One thing to add to Ray's point is that yes, absent wind effects, horizontal group size should increase directly in direct proportion to distance. That is, a group at 400 yards should be 4x the size of the 100-yard group.
However, WIND--even a tiny amount of wind--changes all that because the effect of,90-deg) wind deflection, roughly speaking, goes up with the SQUARE of the distance.,If this seems counter-intuitive, you can plot the drift using a series of right triangles and see how it works). Here, for example is the drift from a 105gr Scenar in a 10mph 90-degree crosswind.
Actual Deflection from 10 mph X-wind
100 yards: 0.58"
200 yards: 2.33" ,Rule of Square result: 4 x .58" = 2.32")
400 yards: 9.63" ,Rule of Square result: 16 x .58" = 9.28")
600 yards: 23.21",Rule of Square result: 36 x .58" = 20.88")
This simply means as you move further out, the effect of the wind goes up dramatically, making it much more difficult to shoot those tiny groups.
I have found over the years of shooting long range that when developing a load for long range its best to move off the 100yd line and start at around 400 or 500yds. If it shoots good there it will shoot good to 1000yds.
I had a 6.5x284 that shot 142s into .3s at 100 and .6s at 200 if I did my job. The same load with 140AMAXs was a consistant .5 load. Now the weird thing is that the 140AMAXs would consistantly shoot tighter at long range.
They would seem to always do better than the 142s under the same conditions. I shot them both side by side on a number of occasions only to come up with the same results.
I shoot at 100yds to get a load that will group around the .5 mark then move on out to 400 or 500yds and start shooting from there on out.
While talking about weird things I went from shooting 142s in my 260 to 140MKs. Now by looking at BCs the 142s should be flatter at long range but guess what?? I use the same exact data out to 1000yds as I did for the 142s. Now why is that???
I had a 6.5x284 that shot 142s into .3s at 100 and .6s at 200 if I did my job. The same load with 140AMAXs was a consistant .5 load. Now the weird thing is that the 140AMAXs would consistantly shoot tighter at long range.
They would seem to always do better than the 142s under the same conditions. I shot them both side by side on a number of occasions only to come up with the same results.
I shoot at 100yds to get a load that will group around the .5 mark then move on out to 400 or 500yds and start shooting from there on out.
While talking about weird things I went from shooting 142s in my 260 to 140MKs. Now by looking at BCs the 142s should be flatter at long range but guess what?? I use the same exact data out to 1000yds as I did for the 142s. Now why is that???
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.