Shooting in the wind

[Vegeta]

Ok on another forum I post on I was just told that a slower round is less effected by the wind, is this true?

 

So for two equal weight rounds fired at different velocities in the same amount of wind, which will be effected more by the wind at a fixed distance. The fast round of the slow round??

[WeihrauchPower]

Ok on another forum I post on I was just told that a slower round is less effected by the wind, is this true?

 

So for two equal weight rounds fired at different velocities in the same amount of wind, which will be effected more by the wind at a fixed distance. The fast round of the slow round??

 

The slow round will be more affected by the wind, the wind has more time to act upon it!

[Vegeta]

Ok on another forum I post on I was just told that a slower round is less effected by the wind, is this true?

 

So for two equal weight rounds fired at different velocities in the same amount of wind, which will be effected more by the wind at a fixed distance. The fast round of the slow round??

 

The slow round will be more affected by the wind, the wind has more time to act upon it!

 

This is what I thought but he disagrees

[JohnGalway]

Is that the forum I'm thinking of Veg?

[Graham M]

Right.. first of all no bullet is affected by ANY wind because no wind could actually blow a bullet off course.

A bullet spins as it travels through the air causing a layer of air to cling to it. If the bullet is spinning in a clockwise direction then the way the wind works is thus-

The bullet is spinning clockwise and is acting in the same way as an aeroplane wind; this is why a spinning bullet will travel further and with more stability.

So any wind coming in from the right will cause it to generate low pressure on the top of the bullet and high pressure on the bottom. This will cause the bullet to climb high and left.

A wind coming from the left will generate high pressure on the top and low pressure on the bottom and will cause the bullet to clime down and right.

This is why you will see targets that are shot in gusty wind showing a group that spreads from 10.00 o‘clock to 4.00 o’clock across the bull.

A faster spinning bullet creates more pressure and therefore moves more in the wind than a slower spinning bullet.

So a fast bullet with a slow twist will move less than a slow bullet with a fast twist. Whereas a fast bullet with a fast twist will also move more than a slow bullet with a slow twist.

I’m going to lie down now as I have a headache.

G.M.

[Vegeta]

The magnus force correct

 

but surely over the same distance a faster travelling bullet (with same twist rate) while effected in a greater way will be in the wind less so it will come out better

[tikkamark]

Interesting thread vegeta Do you know if a bullet weight comes into play at all i mean would the heavier bullet drift less regardless of the speed its traveling at?Would for example a 64grn bullet drift less in the wind than a 50grainer?

[chunk]

Get an anemometer, like an explorer 2(35 quid) measure the wind and work with it using a deflection chart or your own trial and error on targets.

Wind effecting the path of the bullet at 90 dgrees-full value. 45 dgrees-half value etc. Wind is something we all have to put up with but with confidence in your equipment its possible to shoot accurately.

[Graham M]

What a bunch of over complicated ****, No wonder you have a headache. Talk about trying to baffle someone. And by the way, Most aero engineers I have met all say that the schoolboy principle of low pressure above the wing theory is a bunch of **** told to schollboys because its all a bit harder than that to explain.

 

The amount a bullet will drift is simply a combination of its velocity and B.C. When it comes to the real world. If you wanna go into really deep theory we can start on Coreolis effect and the lot. I'm Too proud to google that and cut/paste.

 

eg. In a 10mph wind @ 100 yards my 0.224 cal bullet of B.C. 0.242 doing 3675fps from my 22-250 will drift 0.94"

In a 10mph wind @ 100 yards my 0.308 cal bullet of B.C. 0.508 doing 2830fps from my 308 wil drift 0.66"

 

So whats the complication.

 

You look at the bullets B.C., find out how fast its going and bobs your uncle. The data I have shown is from my ballistics program which has proved very accurate in use for the 22-250 out to 500 yards and the 308 out to 1000yards.

 

The B.C. of a bullet is not mathematically calculated, it is initially approximated from its known shape and mass using established fluid mechanics maths. IT IS THEN TESTED IN THE FIELD by the engineers and this number is often modified to how it reacts in the real world. The actual number is effectively just a percentage of how efficient the bullet is compared to a "standard projectile"

 

For example, my 30 cal lapua scenars have a "published" B.C. of 0.508 but many shooters reckon it to be a little lower, somewhere in the 0.475 region from real world testing and results.

 

Best way to see what happens is just to go shoot some paper, forget the maths, try to learn roughly what wind does for real, OR buy a wind speed meter and carry a laptop. For some good starter info, download a copy of the "pointblank" software and you will see what happens and what changes what. Its a fairly user friendy program, its main drawback is that it doesent give MOA readouts for your come-ups but they can be worked out easily enough in your head.

 

http://www.6mmbr.com/ballistics.html

 

Big heavy bullets with high B.C's are harder to drive fast than smaller less efficient bullets, you get more recoil and eat barrels. You can shoot a 7mm Rem Ultra Mag as fast and flat as a 22-250 with much less drift out to way long ranges but that 100gr of powder, 1000 round accurate barrel life, fierce recoil and medicine ball sized flame tend to make it a hunters gun, not a 1000 yard Br calibre.

 

The reall middle ground in this argument is the 6mm-6.5mm rounds which are the best compromise between frugal costs, good barrel life, minimal recoil and a great compromise on bullet weight/BC/Velocity.

Sorry to have boggled you, but someone asked a question and it was answered in a correct and light hearted manner.

so why do you have to be so bloody bad mannered with your reply.

These forums are full of ****-heads who always want to put others down and when they can’t give an answer themselves they try to discredit those who can.

The answer I gave is correct even if it is of little relevance to vermin shooters. As for the Coreolis effect; yes even that is true which is why rifles once made for the Australian market were once cut with left-hand grooves.

Anyway I’m too pi$$ed off to bother with this any more. If you can’t join in and have a bit of light-hearted banter then stuff you.

G.M.

[WeihrauchPower]

I just dont see the point in giving the guy an answer that is in no way gonna help him. Like for like (identical bullet), the slower one will spend more time in the wind so will drift more, Thats the actual answer to his question to which he himself had the correct Idea anyway (vegeta) and weihrauchpower also gave him the right answer.

 

When I read your answer, I find it hard to make any sense whatsoever from it, especially the aeroplane "wind" bit. True or not as any of that may be, the actual effect in the real world is that there are many more variables you dont mention, the main one being that vertical dispersion is mainly due to longer flight path(the bullet travels in a lateral arc as if it is to hit the centre of the target, it has to be launched to one side of it and allowed to drift in.(in laymans terms, the actual amounts are minimal).

 

This I can tell you from my experience, in real world conditions, shooting VISIBLE projectiles in the wind at International level.

 

ARROWS, they have very high B.C. very low speed and very slow spin when compared to a bullet but shooting them in wind at 100 yards is very similar to shooting long range bullets, you have a lot of windage to compensate for, a lot of drop and its all VISIBLE to the naked eye.

 

Im not saying you are wrong but I dont see how that is going to help him. Velocity and B.C. are the things to understand way before going down the spin road.

 

And just to complicate, he didnt specify whether the slow bullet was shot from a faster twist barrel or not

 

 

 

Well said! No need for a scientific aproach on the simple question that was asked!

[DaveK]

This I can tell you from my experience, in real world conditions, shooting VISIBLE projectiles in the wind at International level with a flag stuck out of my ****. ;)

[Vegeta]

well the problem is i was arguing the fact with someone who was quoting exactly what GM said so I actually found his answer helpful

 

SO just to be 100% clear

 

ok so for a gun with fixed twist rate, 2 identically wieghted and BC rounds are fired. Round A is faster than round B. Conditions for both shots are identical

 

Which is effected by the wind more? According to my ballistics book the answer is the slower round.

[sandy22]

well the problem is i was arguing the fact with someone who was quoting exactly what GM said so I actually found his answer helpful

 

SO just to be 100% clear

 

ok so for a gun with fixed twist rate, 2 identically wieghted and BC rounds are fired. Round A is faster than round B. Conditions for both shots are identical

 

Which is effected by the wind more? According to my ballistics book the answer is the slower round.

 

 

In general, Round B will be affected more, that is to say it will be deflected more at the target. However there are conditions where this may not be the case, particularly where A is just supersonic and B is just subsonic. You may think this is arcane, but bear in mind the vast majority of .22LR ammunition operates in this very area. I suspect your correspondent might be a smallbore target shooter.

 

Sandy.

[dusk2dawn]

Right.. first of all no bullet is affected by ANY wind because no wind could actually blow a bullet off course.

A bullet spins as it travels through the air causing a layer of air to cling to it. If the bullet is spinning in a clockwise direction then the way the wind works is thus-

The bullet is spinning clockwise and is acting in the same way as an aeroplane wind; this is why a spinning bullet will travel further and with more stability.

So any wind coming in from the right will cause it to generate low pressure on the top of the bullet and high pressure on the bottom. This will cause the bullet to climb high and left.

A wind coming from the left will generate high pressure on the top and low pressure on the bottom and will cause the bullet to clime down and right.

This is why you will see targets that are shot in gusty wind showing a group that spreads from 10.00 o‘clock to 4.00 o’clock across the bull.

A faster spinning bullet creates more pressure and therefore moves more in the wind than a slower spinning bullet.

So a fast bullet with a slow twist will move less than a slow bullet with a fast twist. Whereas a fast bullet with a fast twist will also move more than a slow bullet with a slow twist.

I’m going to lie down now as I have a headache.

G.M.

 

That explains the occassional and bl**dy annoying miss on dark and very windy nights, I compd for the windage but not the climb/drop. Interesting I had put it down to eyesight and age, ta for that. :o

 

D2D

[Vegeta]

well the problem is i was arguing the fact with someone who was quoting exactly what GM said so I actually found his answer helpful

 

SO just to be 100% clear

 

ok so for a gun with fixed twist rate, 2 identically wieghted and BC rounds are fired. Round A is faster than round B. Conditions for both shots are identical

 

Which is effected by the wind more? According to my ballistics book the answer is the slower round.

 

 

In general, Round B will be affected more, that is to say it will be deflected more at the target. However there are conditions where this may not be the case, particularly where A is just supersonic and B is just subsonic. You may think this is arcane, but bear in mind the vast majority of .22LR ammunition operates in this very area. I suspect your correspondent might be a smallbore target shooter.

 

Sandy.

 

 

well spotted Sandy, yes he is an issf target shooter.

[dusk2dawn]

SO basically what your saying is that I am getting old and past it, its my shooting and not the wind. :look:

 

For half a day there I felt quite good

 

D2D