Elevation and windage are two factors you need to get right to hit what you are aiming at. How do we compensate for the effect of gravity and wind on our bullet? In this article I’d like to explain and demonstrate the level of thought, diligence and practice we need to invest in establishing, knowing and applying our limits with the rifle. I will also explain some methods that can be used to compensate for windage to ensure that we deliver a humane and responsible kill to the animals that we respect, hunt and harvest.
It is common for hunting rifles to be fitted with a scope that is not designed to allow compensation for bullet drop or wind drift. Such an example is the Type 4 Reticle. This simple system works well if you correctly zero your rifle and know what your maximum point blank range is. Let’s look at my .270 Win firing a 130gn round as a general example. If I zero my rifle to strike 1.5in high at 100 yards, it will result in my set up being bang-on at 200 yards. The next consideration is: What size are the vitals (heart and lungs) on my quarry? And what is my accuracy level?
Let’s suppose that the average measurement of the vitals of a mature deer – let’s say fallow – are estimated in general to be in the region of 8in to 9in diameter. Then we have a start point. Let’s also suppose that my accuracy in the prone position translates to three shots within one inch at 100 yards (i.e. a 1 MOA rifle/shooter). It’s also important to know that you can not only shoot a good group but that you can also hit an intended target. This translates, in the real world, to putting three shots into a one-inch target at 100 yards, repeatedly.
My ballistic app (which we looked at in the second article of this series) can tell me the high and low arc of my projectile throughout its trajectory. So what? Well, we know I am an inch and a half high at 100 yards, bang on at 200 and continuing to drop thereafter. I can see on my app that I have a high of 1.7in at 125 yards and at 300 yards I have a drop of 7.3in. This might suggest that I am within my point blank zero and therefore anything I shoot at out to 300 yards will be hit – but it’s not so simple.
Sticking with just elevation for now, we have a number of factors to consider. The first is that, if I can shoot a one-inch group at 100 yards, can I shoot a three-inch group at 300 yards? Well, the only way to truly find out is to test yourself. Put up a three-inch target at 300 yards on a perfectly calm day with no wind, no pressure and a good rest. Can you put three rounds into that three-inch target? Let’s think positive and say you can. To be diligent, we should then add these three inches to our bullet drop; 7.3 inches + 3 inches = 10.3 inches. If we were aiming at the centre of our nine-inch vital zone, we are now possibly striking almost six inches below the vitals. If we aimed at the top of the vitals then we are possibly striking an inch below the vitals. This could result in a brisket shot – hair and some blood where the animal stood, but the animal nowhere to be found. Perhaps it’s fatally injured, perhaps not, but it’s definitely a situation every hunter should wish to avoid.
This brings us to the next consideration: the anatomy of the animal we are hunting. This means that we as hunters know where the vitals lie and how a change in angle or body position can change where we need to place the shot. There is no better way to learn this than by careful examination of an animal during the evisceration (gralloching) process and by research online, discussions with experienced hunters or books that delve into the matter. Species can differ greatly and the experience from those who are constantly in the field can be most useful.
So back to my .270 example, I can see from my app that at 250 yards I have three inches of drop. I will add 2.5 inches to this (1 MOA) to factor in my accuracy limits. This gives me a potential drop of 5.5 inches. If I have a good understanding of my quarry and I aim at the top of the vitals then I should strike the vitals 3in above their lower edge. Theoretically, this will result in a central heart shot. Having established my point blank zero limit as 250 yards, I should now go and practise on a deer-shaped (and sized) target and confirm that I can place shots accurately in the vitals. This example has hopefully demonstrated the limitations of a scope that has neither elevation nor windage compensation. All this boils down to the fact that a scope with a simple crosshair, correctly zeroed and understood, can be used out to reasonable hunting range in everything but strong winds. It is fair to say that all of our species in Ireland and the UK should be stalkable to within 200 or so yards – but that doesn’t mean that a situation won’t arise where you need the tools and the proficiency to take a shot at farther distance.
“It’s all in the wind.” There are four factors when it comes to rifle hunting that involve wind. The first is its effect on where the animals will be. It’s not unusual for animals to seek shelter from a cold wind front by tucking into a sheltered spot or on the sheltered side of the mountain. Another example is reindeer, who feed and move into the wind, which in turn influences where in their territory they will be found.
The second factor is that you need to get the wind right to prevent the animal from detecting your scent. I like the African phrase of “drinking the wind” as a way to explain that you should keep the wind in your face. If you have spent some time stalking, you will have experienced that feeling of a rogue breeze on the back of your neck in the final stages of a stalk that results in spooking the animals – such is the game.
Third on the wind list is related to the shot, which we will examine in detail here. And the final point is how the wind can assist in the recovery of the animal if you are using a dog.
The general rule for windage is “aim into the wind”. For a wind blowing from left to right, you hold left. This sounds simple but it’s always good practice to have a few little phrases that you can go through in your pre-fire checklist or process – it is surprising what mistakes can be made in the heat of the moment. Practice will help keep these to a minimum.
A modern rangefinder will give you precise information on what compensations you need to allow for distance and shot angle. Some can be programmed to give you a ballistic solution, but when it comes to wind there is very little technology that can give you the important info. You can get technological help in the form of a wind meter, but this will only tell you what the wind is doing where you are. What you need to know is what the wind is doing along your bullet’s flight path. Wind will affect your bullet throughout its flight but will have the more effect as the bullet slows down. If you could pick one point to read the wind for maximum information, it would at 75 per cent of the range – for example for a 400-yard shot, what is the wind doing at 300 yards?
Another helpful hint is that you should imagine that wind behaves like water. If it is funnelled through a narrow channel, it will increase in speed. The terrain between the rifle and the target will influence the direction. Good observation and experience will help you judge this. Invest in a wind meter – they are very affordable these days. Carry it around and during the day stop and judge the wind. Take out your wind meter and see how accurate you were. In time you will improve. If you can judge the wind where you are, you have a good starting point. Now you just need to factor in what effect you think the terrain is having on the wind between you and your target – maybe you are on the crest of a hill getting nailed by a 30mph wind but the deer are tucked behind a spur and there will be no wind effect on the bullet, or vice versa.
Closely observing how the wind affects vegetation at that 75 per cent of the range mark is another element to fine-tuning your wind call. Is that high mountain grass telling you that the wind is gusting, or steady, at 10mph or 20mph?
To improve wind calls I do the following drill on a target at the range:
1. Estimate the wind where you are.
2. Look at the terrain and how it will affect the wind.
3. Pick that spot at 75 per cent of your range and assess what it is telling you about the wind.
4. Compensate for that wind based on your ballistic app outputs.
5. Fire a shot.
6. Observe the strike.
7. Make a note.
Where the bullet strikes will tell you what the wind was doing. For example if the range is 400 yards and my .270 bullet strikes 16cm (six inches) left of my target it tells me there is a 5mph wind blowing from right to left. How did this compare to my estimation? Note what you saw – the terrain that influenced the bullet, how your indicators (trees, grass, vegetation) behaved at the 75 per cent range mark, how the wind felt at your firing position, what your wind meter read. Noting these observations will help you build an appreciation of the effects of wind and help you store the info in your brain for when you need it.
This brings us nicely to the different methods of compensating for wind. There are different methods and different integers (MOA, mRad, fractions of inches, decimals of cm), but basically it boils down to dial or hold. My preference is to hold for wind (I normally dial for elevation) and my unit of choice is 0.1 mRad (basically 1cm at 100m). This means that I use a scope that has a mildot-style crosshair and 1cm clicks. A practical example of this, again using my .270, would be for a target at 340 yards. I can dial 10 clicks or hold 1 mRad. The same is true for windage – dial or hold. The reason I prefer to hold for wind is it gives me more confidence – it is more intuitive (and harder to mess up such as by dialling the wrong way). It also allows you to instantly change your hold if the wind changes or if the range of the animal changes.
My reason for preferring mRad is not only based on the thousands of rounds I have fi red using this system but also because of a formula known as ‘perfect wind’ that allows me to easily and precisely hold for wind at varying distances well beyond hunting range. For this to work, you need to figure out what ‘mile per hour’ your rifle/bullet is. To do this I use my ballistic app and I change the wind value until the numbers make sense. Bear with me…
Again using the .270 as an example, if I input 4.5mph of wind, my 0.1 mRad (1 cm) corrections look as in the table opposite. Notice that the range matches the clicks at this wind speed. If the wind is 9mph, I double my hold, if it is 2mph apply half – you get the idea. Mess around with your wind value until you get values that are easy to remember. Most hunting calibres will vary between 4mph and 6mph and the 1cm/mRad corrections will match out to about 500 yards. Again, if your rangefinder has a choice of metres or yards, you can play with this too to try and come up with a perfect solution.
The final factor to consider is what value that wind is. The value of the wind depends on its angle on the bullet. The clock ray method is often used to explain the application of value but is sometimes mis-explained/understood. You can go into the exact percentage each angle will apply to the wind but I find in hunting scenarios to limit the options to; Full, Three-Quarters, Half, Quarter, or No Value. The thing to get your head around here is:
- A wind from 3 o’clock has full value (10mph = 10mph) and hits the bullet at 90 degrees.
- A wind halfway between 1 and 2 o’clock hits the bullet at 45 degrees but is given a ‘three-quarter value’ (10mph = 7.5mph).
- A wind from one o’clock is given a half value (10mph = 5mph).
- A wind from 12 o’clock is given no value (10mph = 0mph).
The diagram below should help you visualise this.