Coriolis

[stug]

Right here you go
7mm Rem Mag, 162 a-max at 2854 fps

1000yd wind 10mph from 90 degrees shot direction 180 degrees
no coriolis up 24.4 MOA Right 4.7MOA

with coriolis up 24.4 MOA Right 4.9

1000yd wind 10mph from 90 degrees shot direction 0 degrees
no coriolis up 24.4 MOA Right 4.7MOA

with coriolis up 24.4 MOA Right 4.9

1000yd wind 10mph from 90 degrees shot direction 90 degrees
no coriolis up 24.4 MOA Right 4.7MOA

with coriolis up 24.1 MOA Right 4.9

1000yd wind 10mph from 90 degrees shot direction 270 degrees
no coriolis up 24.4 MOA Right 4.7MOA

with coriolis up 24.7 MOA Right 4.9

So not a huge difference max effect of 3" at 1000yds.

 

[Ray B]

Isn't there a Scope I could purchase for 5-6 thousand that will automatically correct for this?

You might get a cheap one for that much- it would need to have a built in GPS unit, weather sensors for air density, humidity, temperature and wind speed and direction. It would also need a compass and inclinometer for direction and attitude of shot. A built in computer would need this information as well as information on one specific bullet BC and mass, along with its velocity and distance to the target. I'm sure there's something like that in the future, particularly for the military, but I doubt the weight would be of carryable proportions, even if the price was no object for us civilians.

 

[Rob404]

You might get a cheap one for that much- it would need to have a built in GPS unit, weather sensors for air density, humidity, temperature and wind speed and direction. It would also need a compass and inclinometer for direction and attitude of shot. A built in computer would need this information as well as information on one specific bullet BC and mass, along with its velocity and distance to the target. I'm sure there's something like that in the future, particularly for the military, but I doubt the weight would be of carryable proportions, even if the price was no object for us civilians.

I suppose I'll have to start working out

 

[cagkt3]

If anyone is really interested, I had a friend who does F1 matches turn me onto to this app - BalllisticsARC by GeoBallistics. It's a free app - plug in your rifle and ammo info and it will create dope sheets (table of MOA or MIL adjustments) for you. The have many of the factory loads pre-loaded in their database, or you can add your own data (BC, muzzle velocity etc). The only rifle data you need is twist, scope height, zero range etc - the basics. Also has a mapping/GPS function so you can see aerials of the range. You can also add a wind and/or weather meter from the same company, for $45 or $90 respectively. The wind meter obviously takes the wind into account and adjusts your dope sheet accordingly, while the weather meter takes temperature, humidity, atmospheric pressure etc into account.

They also have a premium version ($15 I think) which allows you to save things to the map (i.e. your home shooting range) and use your phone as a range finder for long range shots if your handheld rangefinder can't handle anything past 600 yds like my old Nikon.

https://geoballistics.com/

 

[BigJohnx13]

Coriollis really comes into play when cannons (artillery) shoot farther that 10 km. The Germans found out the hard way when using their Railguns

 

[Red Leg]

When we fire artillery, a large number of issues come into effect ranging from met (wind speed and air density along the full trajectory of the round - remember an artillery round may rise tens of thousands of feet to hit a distant target - so a hand-held wind meter is useless), internal ballistics (the peculiar aspects of a particular howitzer barrel - i.e wear of the rifling), powder temperature, coriollis, and of course accuracy of the known position of the firing weapon. To remind, artillery is firing at targets well beyond the visibility of the gun crew. We use to work all the gunnery out manually with slide rules and graphic ballistic tables and the howitzers were literally surveyed into position. Computers, naturally, have sped that up enormously. Also, depending on the target and weapon, GPS sensors can be fitted as a fuse to the round which will make final corrections to het the desired impact point. Maybe Hornady can cum up with a micro-GPS equipped bullet for the long range crowd.

 

[Mr. 16 gauge]

OR......................
......instead of worrying about "long range shooting", you could just work on your stalking skills.........and go "hunting".

.............just sayin'

 

[fourfive8]

OR......................
......instead of worrying about "long range shooting", you could just work on your stalking skills.........and go "hunting".

.............just sayin'

Well said!!

 

[lockingblock]

It is 99% bull.

Frank, over on snipershide, has written about it a good bit. You can debate it all day along with whether you are shooting East/West/North South and what season it is vs the rifling twist direction and whether it is going to climb/pull your bullet a certain direction...

In the end, unless we are talking ELR shooting (beyond a mile), it isn't going to matter. In the hunting world, nobody should be shooting far enough for any of this to matter.

If you really want to dig into it, download a basic ballistic solver like applied ballistics, buy the books for it, a chrono, and walk through trueing it up. It will give you all the data you could want, well beyond the capability of most shooters. A ballistic solver...even the IPhone versions...will do more for you than just about any other piece of data, assuming you have valid data to put in (actual BC of bullet, velocity, temp, altitude, and so on).

 

[fourfive8]

mostly academic except for really long range shooting- like biiiig artillery. Always much confusion and misinformation floating around the coffee shop on this one! Also, there is a big difference between the Magnus Effect (spin drift) and the Coriolis Effect.

 

[edward]

think ill stick to hunt and stalk.

 

[Rule 303]

No, it's not a high or low; it's a side push, so north of the equator you'd adjust to one side and south of it you'd adjust to the other, but I forget which way is which. Best to have a spotter, fire one shot, see impact, adjust and hit with the second.

Correct. The poms had the opposite twist to others as they believed most of their battles would be fought in the Southern Hemisphere. The direction of rotation of the bullet helps dampen the Coriolis effect or increase it if the spin is in the wrong direction. From jaded memory the effect on a 303 bullet at 1000yds was a couple of inches to one side of the point of aim. Thats from very jaded memory so probably not exact.

So this is really not going to effect most of us at all. Group size at that range is bigger than the Coriolis affect. As said by somebody earlier in the thread unless you are shooting a mile or more there are greater things to worry about.

 

[Ridgewalker]

Probably should have considered this on my Cape buffalo at 30 yards. Still, you guys have added some interesting info to my old grey matter.
Thanks...now I have a headache!

 

[fourfive8]

The Coriolis effect is so small for small arms ballistics it's really not a factor. The ranges are relatively short with relatively short flight times and the bullets stay well down in the atmosphere. I think the confusion is that most are using the term Coriolis effect but really referring to the Magnus effect- which is spin drift. Spin drift is measurable for small arms bullets... albeit fairly small for stable-in-flight conventional bullets. The angle built into the rear sight (Buffington sight) on an M1884 US Springfield 'trapdoor' rifle is an example of compensation for the Magnus effect (spin drift) over the max range of the rifle- up to about 2000 yards.

The Coriolis effect is measurable where a big bullet is shot over a long distance with a relatively long flight time and trajectory that is well up into the atmosphere... like a big artillery projectile. During that flight time, the "ground" under the projectile measurably changes position because of the earth's spin. The direction of projectile's travel relative to the direction of the earth's spin determines amount and direction of the effect.

 

[Rule 303]

fourfive8, I am talking about Coriolis not the Magnus effect. As I said the Poms had the different direction of rifling twist to use the Magnus effect to counteract Coriolis effect for the southern hemisphere. I don't know why they did that, given the accuracy of the day and the distances that they shot at. Maybe it was for the Volley Fire, where the shooting is group shooting out to a mile. Idea was to bring plunging fire into dead ground where troops would form up, even though there was stuff all accuracy in that form of shooting.

As you and others have said it is a worry for Artillery.

 

[fourfive8]

Yes, that was the purpose for the spin drift compensation angle on the staff of the Buffington sight on the M'84 trapdoor... extreme ranges for concentrated plunging, volley fire.

 

[Chago]

Military Sniper myself, no one on this forum ever needs to worry about Coriolis effect. And if you do, your shooting way too far for your skill if you even have to ask if you need to account for Coriolis.

 

[Ridgewalker]

Military Sniper myself, no one on this forum ever needs to worry about Coriolis effect. And if you do, your shooting way too far for your skill if you even have to ask if you need to account for Coriolis.

Welcome to the forum Chago! It will be interesting to hear from your experience. Me, I don’t shoot well enough to try over 400 yds nor in over 10mph winds. Pretty much makes most days in Wyoming antelope hunting a no go!

 

[Buckdog]

You guys now just stop being cheap and go get a wind meter and ballistic computer for that next 200yd shot at a kudu and tell him to stand there while you get coriolis worked out for the shot fugured out. Me I will just shoot him

 

[Hogpatrol]

I think one should stalk and get closer. That way your lousy shooting skills won't be exposed and you'll be able to find out how many shots a wildebeest, kudu, elan, gemsbok or other large animal will take before falling over dead.