- Thread starter huntdog13
- Start date
Touch of spin drift, maybe a touch of Coriolis, maybe some unaccounted for wind.
Spin drift and coriolis are a non issue at those ranges. you won't see them have effects until 1500. chances are it's either wind that is not accounted for or it's the shooter.
I gotta disagree. 600 yards seem to be where those things start to have an noticeable effect.
My rifle has .15 mils of spin drift at 600 yards (about 3") and depending on what direction you are shooting, you could see a small amount of drift to the right due to Coriolis effect.
Spin drift and Coriolis increase linearly with range, it is not a light switch, where at one range they have no effect and then magically a yard later they play a part.
Last edited:
Spin drift to the right for a .308 178 A-max @ 2640 fps with a 1-10" twist @ 600 yards is 3.2 inches.
Coriolis does drift to the right in the northern hemisphere, how much depends on latitude and direction of fire, and it does have an effect even at 600 yards, even if it may be very small.
This is verifiable fact.
Your meme is the most ignorant thing I've seen all day.
Coriolis does drift to the right in the northern hemisphere, how much depends on latitude and direction of fire, and it does have an effect even at 600 yards, even if it may be very small.
This is verifiable fact.
Your meme is the most ignorant thing I've seen all day.
Last edited:
shooting beyond 500 yards
If you're seeing that much horizontal spread without wind then you have an error during trigger pull. FACT! You're not going to see that much drift at 600yds from coriolis. I don't see that much at 1000. Coriolis doesn't have as much of an effect north and south as it does east and west. The earth drags it's atmosphere. At 1000 I may see an inch of spin drift. 1 inch! I suggest you go plug a few scenarios into FFS and see what you come up with.
If you're seeing that much horizontal spread without wind then you have an error during trigger pull. FACT! You're not going to see that much drift at 600yds from coriolis. I don't see that much at 1000. Coriolis doesn't have as much of an effect north and south as it does east and west. The earth drags it's atmosphere. At 1000 I may see an inch of spin drift. 1 inch! I suggest you go plug a few scenarios into FFS and see what you come up with.
shooting beyond 500 yards
Darkside, have you seen any of this short range Coriolis effect south of the Hungarian border, or in your experience could what he is seeing be a phenomena limited to Western Europe and Sub-Saharan Africa?
... Or, could it be that on a square range his rifle behaves differently because it knows it is shooting for score?
Darkside, have you seen any of this short range Coriolis effect south of the Hungarian border, or in your experience could what he is seeing be a phenomena limited to Western Europe and Sub-Saharan Africa?
... Or, could it be that on a square range his rifle behaves differently because it knows it is shooting for score?
Last edited:
What do I know, maybe his bullet just falls asleep.
shooting beyond 500 yards
It is FACT if the bullet is not asleep yet it can't have spin drift so I just refuse them the ability to go to sleep. I use a proprietary coating of Caffeine powder, also Coriolis effect can be minimized if you only hand load with bullets made in your Hemisphere, hence Sierra and Hornady popularity. The evidence is undeniable.
bender out.
It is FACT if the bullet is not asleep yet it can't have spin drift so I just refuse them the ability to go to sleep. I use a proprietary coating of Caffeine powder, also Coriolis effect can be minimized if you only hand load with bullets made in your Hemisphere, hence Sierra and Hornady popularity. The evidence is undeniable.
bender out.
OP, you asked an honest question so don't feel like we're slamming YOU. if you're getting horizontal drift it is usually 2 things, wind or trigger manipulation. if you were shooting strait at 500 then I'm guessing the problem could be wind that was unaccounted for. wind is a tricky SOB. Just because you don't see/feel it closer to you doesn't mean it's not blowing down range.
OP please fill out your profile.
As has been mentioned already above......trigger press and wind
As has been mentioned already above......trigger press and wind
Spin drift is a difficult animal to predict. Yes, in a laboratory environment, it is an easy phenomenon to produce. Given right hand twist and a perfect departure from a barrel, it will drift to the right as it flies down range. The drift at 1k could be anywhere between 6 and 12 inches. However, none of us shoot in a perfect lab environment. Imperfections in the crown that differ from barrel to barrel could cause variations in departure of bullets between guns. Initial yaw rates at the muzzle can cause error up, down, left or right. The bullet will precess and nutate along the entire trajectory and any observed drift ("spin drift", or otherwise) is just the effect of the average yaw of the bullet with respect to the flight path. On top of all this, an imperfect zero at 100 or 200 yards can initiate a "drift" that adds to or takes away from what you think might be spin drift. And even when you've got all those details figured, wind is so variable and difficult to predict, you could have all your gyrosopic anomolies accounted for and then miss by a couple feet due to a bad wind call. So any error witnessed that seems to appear suddenly is not going to be one of the minute details of gyroscopic or coriolis effects, its more likely wind that you didn't know was there between you and the target.
Two words, Lunar Drift... Accounting for it can be an extra solar experience.
Last edited:
What load, are you shooting? Could it be going subsonic at 550? OR, maybe it' s a psychological problem. You may be "tensing",because you,re "taking the next big step"in the game. Could be cant. some learned members are mentioning the coriolis, and spin drift. BAAHh HUMBUG! Any "educated"conspiracy guy knows "THEY" have been secretly burying nuclear waste all over the country. When I hear some one mention the coriolis affect, I put a pin on my map at their location. YUP! There's another dump site! Such dense material has a profound affect on the gravitational field. Also, the affect of the radiation on the local gene pool!
Ok now I want to see someone shoot their rifle upside down!!! Right meow!
shooting beyond 500 yards
Tried it this last weekend and guess what? Nope, still no spin drift. I must be doing it wrong.
Tried it this last weekend and guess what? Nope, still no spin drift. I must be doing it wrong.
Last edited:
If it's a 308, there's ALWAYS wind past 500Y.
ALWAYS.
The bullet is better at detecting it than you. Instead of second guessing the bullet, why don't you just listen to what it's saying?
--Fargo007
ALWAYS.
The bullet is better at detecting it than you. Instead of second guessing the bullet, why don't you just listen to what it's saying?
--Fargo007
Huntdog
Sounds like you are basing this past 500 on one shooting session or range trip? A single data collection does not tell us much, several data sets will start giving us a picture. Always go to the range either reinforcing your data or update it. From what you post it is most likely wind or some trigger press issue. No I repeat No spin drift, Coriolis effect, magnetic anomalies, solar flare/ sunspot count, time warp effects are of any concern before 1200 yards. Your wind call will mask any of these at mid range.
Sounds like you are basing this past 500 on one shooting session or range trip? A single data collection does not tell us much, several data sets will start giving us a picture. Always go to the range either reinforcing your data or update it. From what you post it is most likely wind or some trigger press issue. No I repeat No spin drift, Coriolis effect, magnetic anomalies, solar flare/ sunspot count, time warp effects are of any concern before 1200 yards. Your wind call will mask any of these at mid range.
shooting beyond 500 yards
Balistic ae dope for federal 175 smk in .308 shows .27 moa spin for 1000 yards and that's with 0 wind. The kestrel ab is more accurate than any dope app. as long as the data is input right. Apps and kestrels work great but I don't think there's a such thing as perfect conditions.
Balistic ae dope for federal 175 smk in .308 shows .27 moa spin for 1000 yards and that's with 0 wind. The kestrel ab is more accurate than any dope app. as long as the data is input right. Apps and kestrels work great but I don't think there's a such thing as perfect conditions.
Last edited:
Find me a guy who figures spin drift for anything under 1000. I ain't buying it.
1200 yards I just dial for wind no spin for .260
OP,
Start recording your calls and shots in a data book. Annotate all conditions. Eventually, you will be able to understand most every reason there is for the bullet not going where aimed.
Start recording your calls and shots in a data book. Annotate all conditions. Eventually, you will be able to understand most every reason there is for the bullet not going where aimed.
You're most likely tilting right... right handed shooters tend to tilt right, and even if you're a lefty you still may be tilting right a bit. If you don't have a scope level (anti-cant level), that's the most likely problem. If you do have a level, it may need to be trued to gravity so that it indicates correctly.
If you have a level and you know it's trued, then your scope may be getting some windage drift as you dial up in elevation (it happens a lot)...
If you're not dialing up and simply using hold-over, your reticle may be slightly crooked.
But it's not spin drift or coriolis, we can rule that out.
On the wind... it doesn't take a lot of wind to move a bullet. You can't see the evidence in the trees and grass from a 2 mph wind in most instances (you'd need good flags or have good mirage and read it correctly)... so yes, it could still be wind. A 2 mph wind can move you 2 MOA at 1000 yards with many 308 win loads... and it'll move the 6mm's and the 6.5's more than an MOA (they're not immune, they just drift about 30% less on average).
Dan
If you have a level and you know it's trued, then your scope may be getting some windage drift as you dial up in elevation (it happens a lot)...
If you're not dialing up and simply using hold-over, your reticle may be slightly crooked.
But it's not spin drift or coriolis, we can rule that out.
On the wind... it doesn't take a lot of wind to move a bullet. You can't see the evidence in the trees and grass from a 2 mph wind in most instances (you'd need good flags or have good mirage and read it correctly)... so yes, it could still be wind. A 2 mph wind can move you 2 MOA at 1000 yards with many 308 win loads... and it'll move the 6mm's and the 6.5's more than an MOA (they're not immune, they just drift about 30% less on average).
Dan
Yep
What cartridge and twist are you using?
A 175-grain 30-cal Sierra Match King should only drift a half minute at 600 yards (with a 10-twist barrel at 4500 feet above sea level).
Is your vertical cross hair plumb (straight up-and-down) with your bore axis?
A 175-grain 30-cal Sierra Match King should only drift a half minute at 600 yards (with a 10-twist barrel at 4500 feet above sea level).
Is your vertical cross hair plumb (straight up-and-down) with your bore axis?
TacticalBoltKnob is correct. Error factors: ammo, wind, shooter, spin drift (a right-twist barrel in the Northern Hemishpere demonstrates spin-drift the same whether it is right-side up or upside down, since the spin is called "right spin" but is actually clockwise, which does not change when the rifle is upside down), coriolis (lateral movement to the right in the Northern Hemisphere, the same at one geographic location no matter direction of fire), vertical angle, vertical wind (due to local terrain), vertical coriolis (dependent on direction of fire, and most noted when shooting directly east or west; same effect in Northern as in Southern Hemisphere), elevation change due to horizontal wind component, and atmospheric change (temp, pressure, humidity, elevation; these are all air density issues). We should be shooting "left-twist" barrels in the Northern Hemisphere, since spin drift would just about totally balance lateral coriolis, and the Southern Hemisphere blokes should shoot right twist barrels for the same reason. Somebody who knows, correct any errors, please. Just to totally confuse you, I do agree with Darkside that these are non-issues at the intermediate ranges, since shooter error and wind are such large errors that the other errors we are looking at "disappear" in the fog of group size related to shooter and wind errors. You just have to know that they are there, apply them to your calculation (i.e., enter them in your computer/ballistic program), and know that making those [relatively small] corrections will get you closer to the center of the target.
Huntdog13, here are a couple of things that you can do.
Get a target that is 20 inches high or more. Put a good aim point on the bottom edge of the target. (This assumes a 200 yard zero) Place the target at 200 yards. Crank in your 300 yard setting and shoot a 3 shot group. Crank in your 400 yard setting and shoot a 3 shoot group. Same for 500, 600, and 700. (a 20-inch high target should be good out to your 700 yard setting) If they are all in a vertical line then the scope is working correctly. If the line through the group centers is canted or if is vertical up to 500 then goes off to the left -- you have your solution.
Go to your range and put up wind flags and watch direction. If you don't have proper flags, buy some pink, green, or orange engineer tape, poke a stick in the ground and tie some tape to it. Flags will give you speed and direction. Direction is obvious. Speed can be estimated from the angle between the stick and the tape.
I walk downrange with a Kestrel and take some wind velocity measurements. I measure every 100 yards or so looking for a change in speed or direction. One range has trees, look at the leaves and limbs. Another has trees and corn, I watch the corn. If grass, I watch the way the grass blows.
Based on the limited information in your post, I suggest that you look for a spot between 300 and 600 where there is a break in the left berm or a spot where the wind rolls in from the left.
Mirage is great for light conditions -- less than 5 MPH. Above that, I think the mirage just runs and I cannot get much out of it. You can construct a mirage board. Paint a half-sheet of plywood with alternating 2-inch or 3-inch black and white horizontal stripes. Stand it up at 500 or so. It really makes the mirage easy to see.
Nobody brought this up so here goes - is this behavior consistent (you have seen it over several shooting sessions at a particular range or on different ranges) or did you start to shoot 700 on some day and the impacts went to the right? If this was the first try past 500 then could the conditions have changed and you didn't pick it up?
I was out shooting steel yesterday; range orientation is SSE to NNW. There was a pretty good breeze coming in from the southwest - sometimes the right-side flags were standing right out. Left-side flags were not showing much, sort of whooping around, sometimes the left-side flag would show some wind from the east. There was a hunk of engineer tape out at the far end that blew the wrong way. That is, when we had a good breeze from the west, the tape was showing a good breeze from the east. We decided that the far targets were in a pocket of trees and the wind was swirling and the bullets were snaking their way to the targets. That swirl was giving us a lot of horizontal - in some cases 0.5 mil on the target. I was shooting at a 24-inch plate at 1,000. I would hold center and get a hit. Repeat, hit. Hold center and see the dirt fly off to the right. Check the flags, I missed a condition. Condition holding, hold left edge and get a hit. Condition holding, hold left edge - flags looked the same - and miss to the left. Wind is a cruel mistress.
Get a target that is 20 inches high or more. Put a good aim point on the bottom edge of the target. (This assumes a 200 yard zero) Place the target at 200 yards. Crank in your 300 yard setting and shoot a 3 shot group. Crank in your 400 yard setting and shoot a 3 shoot group. Same for 500, 600, and 700. (a 20-inch high target should be good out to your 700 yard setting) If they are all in a vertical line then the scope is working correctly. If the line through the group centers is canted or if is vertical up to 500 then goes off to the left -- you have your solution.
Go to your range and put up wind flags and watch direction. If you don't have proper flags, buy some pink, green, or orange engineer tape, poke a stick in the ground and tie some tape to it. Flags will give you speed and direction. Direction is obvious. Speed can be estimated from the angle between the stick and the tape.
I walk downrange with a Kestrel and take some wind velocity measurements. I measure every 100 yards or so looking for a change in speed or direction. One range has trees, look at the leaves and limbs. Another has trees and corn, I watch the corn. If grass, I watch the way the grass blows.
Based on the limited information in your post, I suggest that you look for a spot between 300 and 600 where there is a break in the left berm or a spot where the wind rolls in from the left.
Mirage is great for light conditions -- less than 5 MPH. Above that, I think the mirage just runs and I cannot get much out of it. You can construct a mirage board. Paint a half-sheet of plywood with alternating 2-inch or 3-inch black and white horizontal stripes. Stand it up at 500 or so. It really makes the mirage easy to see.
Nobody brought this up so here goes - is this behavior consistent (you have seen it over several shooting sessions at a particular range or on different ranges) or did you start to shoot 700 on some day and the impacts went to the right? If this was the first try past 500 then could the conditions have changed and you didn't pick it up?
I was out shooting steel yesterday; range orientation is SSE to NNW. There was a pretty good breeze coming in from the southwest - sometimes the right-side flags were standing right out. Left-side flags were not showing much, sort of whooping around, sometimes the left-side flag would show some wind from the east. There was a hunk of engineer tape out at the far end that blew the wrong way. That is, when we had a good breeze from the west, the tape was showing a good breeze from the east. We decided that the far targets were in a pocket of trees and the wind was swirling and the bullets were snaking their way to the targets. That swirl was giving us a lot of horizontal - in some cases 0.5 mil on the target. I was shooting at a 24-inch plate at 1,000. I would hold center and get a hit. Repeat, hit. Hold center and see the dirt fly off to the right. Check the flags, I missed a condition. Condition holding, hold left edge and get a hit. Condition holding, hold left edge - flags looked the same - and miss to the left. Wind is a cruel mistress.
At the gun club that I often shoot at the wind to 400 is a lot different than the wind at 500 and beyond in both speed and direction.
I was dialing in a 2 mph wind for 500 yards and a 18 mph wind at 700 today.
I was dialing in a 2 mph wind for 500 yards and a 18 mph wind at 700 today.
Last edited:
Dan, what's the best way to true up a level? I've wondered this mounting scopes to get reticles perfectly aligned also.
Thanks in advance,
Mark
just put the vertical crosshair on a known plumb line... (hang a rope in a tree with a weight on the end of it, or use a radio tower or something you know is plumb to gravity), and index the scope level to that position.
as far as leveling the scope to the rifle itself, that's something that you can just "eyeball" and get close enough. having the scope perfectly level to the rifle's action isn't all that important (some shooters actually mount scopes with a certain amount of cant to make the rifle more comfortable to shoulder, while allowing the scope's reticle to remain level to gravity). as long as the scope is zeroed in the level position, and held level for all shots downrange, the trajectory will stay on the correct sight plane to keep the shot from drifting left or right (as it will if you tilt the scope left or right). I did this crudely illustrated article (I used MS paint) several years ago, which may help: Canted scope or canted rifle? in Rifles and Scopes... Forum
we use props in the long range rifle classes to show folks what's going on with the trajectory when they tilt the rifle. this can be kinda hard to communicate in writing in a forum such as this... but hopefully the article will help.
Dan
tagged thanks for the info gents
Hey Tactical Douche Knob- I see you've become quite an expert on spinning your coriolis since you joined six months ago and were dreaming of shooting past 300 yards. After our last exchange I was hoping you had packed up and gone back to ARF15.com or whatever bridge in WI you crawled out from under. You must have finally saved up enough money to go to that really expensive shooting facility in WI run by those greedy people who have the audacity to try to make a living running a shooting complex. Was it there or "out in the west" that you garnered your expertiese on coriolis spinning in the northern hemispheres? The problem with posting in the "Stupidist Questions" section is that you will often get "stupidist answers" for toe-jam whiners like TDK. Listen to DS6 he's wired tight.
Makes sense on the plumb line, interesting thought about intentionally mounting with some cant to make the shooting position more comfortable, and great article - I had never thought about it like that. Very well written, and very helpful. Thanks!
Mark
That sounds like a bad ass excuse to use when I am missing shots around folks who might be newer to LR shooting.
Then you sound like a tool to those who are not new......
Could be failure to watch the movie "Shooter" enough times in a row... 
I read somewhere that if your bore has some wear on it, it can cause the bullet to drift.
Man, I'm really stepping into this one. But I gotta know what's up with this.
Bear in mind before you flame me that I'm a 3 gunner/hand gunner new to long range rifle. My long range rifle experience consists of NRA High Powered Rifle with an M1A and irons.
So according to my app (Ballistic AE), my .308 175 SMK's at 2632fps have a Spin Drift of 3" at 600yds, 6.4" at 800yds, and 11.5" at 1000yds.
Is this data wrong? Is it some pie in the sky guesstimate that doesn't bear out on the the range? Or no one cares about 3 to 6.5"s inside 800yds?
Bear in mind before you flame me that I'm a 3 gunner/hand gunner new to long range rifle. My long range rifle experience consists of NRA High Powered Rifle with an M1A and irons.
So according to my app (Ballistic AE), my .308 175 SMK's at 2632fps have a Spin Drift of 3" at 600yds, 6.4" at 800yds, and 11.5" at 1000yds.
Is this data wrong? Is it some pie in the sky guesstimate that doesn't bear out on the the range? Or no one cares about 3 to 6.5"s inside 800yds?
Me too!
I think the point guys are trying to make is that your error in reading the wind will eat up any spin-drift you may or may not try to account for. Basically, when you can read wind within 1/2 MOA, start worrying about spin drift.
Similar threads
Advanced Marksmanship Optimum 6.5 Creedmore bullet weight hunting small game long range
