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Sighting it in: A guide to getting on target

By Matthew Cameron

There are many items within the various shooting disciplines that are very much suited to individual taste; sighting in rifles is one such issue. I understand that there are many different ways of achieving the same result. In this article I am merely specifying several personal ways of carrying out this procedure, hopefully it may provide some guidance to less experienced riflemen.

 

Where once telescopic sights were unusual in this day and age, open sights are rarely seen except perhaps in some shooting disciplines. In addition, there are many versions of the same theme which may or may not cause the new rifleman some confusion.

 

There are however a few shortcuts which may save some valuable time. You should do a certain amount of research based on the intended use before committing your hard earned cash on a suitable telescopic sight.

 

Before you buy there are a couple of decisions regarding the proposed sight that relate to the calibre of the rifle and its range of use as the requirements of the hunter or shooter who wishes to hunt pigs and/or deer are vastly different to those of the varmint hunter. Again, the deer hunter who seeks to engage his quarry at longer ranges will have different requirements.

 

The other question is whether the sight should be of fixed power or a variable. The author is well aware that such decisions are a veritable minefield of personal choice and some misinformation. What suits one may not suit another; in addition the range of choice available today is immense.

 

“Before you buy there are a couple of decisions regarding the proposed sight that relate to the calibre of the rifle and its range of use...”

 

However, some general suggested guidelines are in order. If the rifle is to be used for general hunting with perhaps a rifle in .270 Winchester calibre (or similar) a 3-9x variable power telescopic sight could be considered useful.

 

It can be wound down to 3x power when bush stalking or in scrub and turned up to 9x power for longer shots. A variable type sight allows you to cover several types of use and is thus more flexible.

 

If the sight might be used for spotlighting do not get very fine cross hairs as they will be very hard to see under the light. Perhaps the most useful reticule is the plex type; the cross hairs are thicker at the outer edges and naturally centre the eye on the target. For personal preference, the author prefers sights that are plain and uncluttered. Another suggestion for hunting is a plain 4x or 6x.  

 

Example of Plex (Left) and Duplex reticles.

 

Target shooters including those addicted to benchrest usually have specific requirements and are outside this discussion. For the varmint hunter, shooting small targets at longer ranges other considerations are applicable, mainly in relation to the rifle/ cartridge combination.

 

Usually those interested in shooting at longer ranges have already dipped their toes in the water so to speak and have started the process at much shorter ranges initially and then proceeded to cartridges with greater powder capacity and hence velocity.

 

There are various mounting systems for sights; the author suggests some research to see what suits you. Within our family we have used the same brand name bases and top mounts for over thirty-five years without any trouble; it was an initial recommendation from a gunsmith.

 

“Before you buy there are a couple of decisions regarding the proposed sight that relate to the calibre of the rifle and its range of use...”

 

Once you decide on the bases the top mounts will be selected depending on the diameter of the telescopic sights main tube, usually 25mm or 30mm, if in doubt measure with a pair of calipers. Most gun shops carry a fairly extensive range to suit most rifles.

 

Usually base mounts have either screws or Allan keys to attach them to the rifle; it pays to have the correct tools to make the job easier, a basic set of gunsmith screwdrivers will be a wise investment as will a set of Allan keys from your local hardware or automotive discount store. 

 

Some suggest that Loctite or a similar product will hold the bases onto the rifle and prevent them coming loose; it is probably a wise investment.

 

Optics need to be mounted securely to ensure consistent accuracy.

 

The vertebral and lateral adjustments on modern sights are usually via target knobs, for older sights some use slots in the heads which require a coin or a correct size screwdriver to alter the settings.

  

When you get everything assembled on the rifle it is important to ensure that the horizontal cross hair of the sight is at right angles to the axis of the bore when the rifle is held in the normal firing position, tighten the top mounting screws just to the point where you can still turn the main tube, it will become readily apparent.

 

When you are satisfied with the correct position tighten all the screws. Now we are ready to fire a few shots to get the sight picture correct for the ammunition you are using.

 

Bore sighting bull for use at 25 yards.

 

The initial requirement is to align the sight with the bore of the rifle so that our initial shots will be on the paper target. If we are using factory ammunition all we seek at this stage is the ammunition that provides the best group, you may have to change to another brand.

 

All we must do then is ensure that the impact on the target agrees with our ballistic chart. For the reloader who is developing his own ammunition this same process will get his initial loads on the paper target, we can alter the point of impact once the decision is made as to which load is the most accurate.

 

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Just because you mounted your telescopic sight on the rifle it is highly unlikely that it is totally in alignment with the rifles bore, the solution is bore sighting. It may be done relatively quickly with minimum equipment. For a target you need a 3 inch or so bull on plain white paper.

 

To support the rifle you need a bipod, sandbags or a large cardboard box with V slots cut in two sides. Place the bull some 25 yards from the supported rifle and remove the rifles bolt.

 

Sight through the bore until the round target is centered. Without moving the rifle adjust the cross hairs of the sight to coincide with the centre of the bull, this should get you on the target. 

 

The next step is to shoot the rifle at 25 yards with your normal ammunition, if you use factory ammunition the choice is easy, if you are a reloader the author would suggest a starting load you would use during load development. The initial shooting distance needs to be 25 yards for the simple reason that nearly all projectiles cross the line of sight at this initial distance.

 

Most telescopic sights can change the point of impact both laterally and vertically in either 1/8"or 1/4" clicks of the adjustment screws or in some sights, knobs. Note that these distances are applicable at a normal 100 yards, at 25 yards they will only have 1/4 of this value.

 

Centre the cross hairs of the sight on the centre of the target and shoot one round. Impact should be reasonably close to the centre of the bull. If not, centre the cross hairs on the bull again and use the vertical and horizontal adjusting knobs/screws to place the cross hairs over the first projectiles impact point.

 

Shoot another round; this will be much closer to the centre of the bull. Now it is time to move the target out to 100 yards and if you are a reloader the load development process can begin. Initially we do not concern ourselves just where the initial groups land on the target, with increasing powder charges and possibly different projectiles the groups will move.

 

It is not important where the groups land initially, we are looking for smallest group size.

 

At this stage what we are really interested in is group size. Once we have decided on the load to be used now we can adjust the impact on our paper target to match the ballistic chart. It is suggested that a target with one-inch squares is very useful at this stage.

 

In the days when personal chronographs were virtually unknown it was suggested that a hunting rifle should be sighted in with the projectile impact between 1”-3” above the line of sight at 100 yards, certainly the author continues to use this method for all of his hunting rifles, in simple terms it works. It is in the author’s opinion useful for cartridges such as the .222 Remington or .223 Remington where shots may not exceed 300 yards.

 

We can use modern technology to see how accurate this method is. As a representative example we will use the .270 Winchester cartridge firing a 130gr soft point Interlock projectile perhaps at some 2900 fps. out of a new barrel.

 

If we feed these figures into a computer program such as Load from a Disc (Discontinued, see note below) we find that the projectile is no more than about 3.5" about the line of sight out to 250 yards, at 300 yards it is approximately the same distance low.

 

If we apply the same logic to the .223 Remington cartridge using a 55gn projectile with a B.C. of .267 at 3100 fps. The projectile rises a maximum of 3.6" above the line of sight and is the same distance low at 300 yards.

 

It is safe to assume that the zero range for any number of projectiles is somewhere between 240 yards and 300 yards depending what the B.C of a projectile is. Using this method we do not have to know what the cartridge velocity is. Any reasonable ballistic program will prove these figures.

 

Matthew's 100/200yd Benchrest rifle. The scope has a maximum magnification of 36x for precise projectile placement. Note portable bench and rifle supports. 

 

From now on is where the difference emerges between the hunters using larger calibres and the varmint hunter. Having carried out the process of load development it is time to use the initial cartridges that you have loaded to get the sight picture correct, as with factory ammunition there will be a specific height on the target where we want our projectiles to impact on.  

 

Perhaps a majority of varmint hunters have started out with a .222 or perhaps a .223 Remington cartridge and progressed from there; or in this day and age perhaps a .204 Ruger. It is not a bad base to start from, reloading such cartridges is cheap and a suitable telescopic sight is perhaps a 4-12x variable which is adequate for the calibres and useful out to 300 yards or thereabouts.

 

Once we start extending the range beyond 230-250 yards or so, there is a requirement for a rangefinder and a ballistic chart as few riflemen can judge distance accurately beyond those distances. The most accurate and easiest to use are the various electronic devices, these are not perfect but they are far better than the human eye.

 

Ballistic chart for .22-250 Remington.

 

When we step up to this level of varmint cartridges other issues become apparent; in the main I am referring to the .22-250 Remington .220 Swift and 6mm Remington. All three are well known and more than adequate performers out to perhaps five hundred yards/metres (take your pick) although the Swift is possibly out of favour with the shooting public.

 

However, at these extended distances we also have a requirement for more powerful telescopic sights with extra magnification, this allows for more precise aiming.

  

There is some discussion as to exactly the power you require; perhaps a variable somewhere in the region of 6-24x will cover a lot of ground. Just be aware that high magnification on hot days will pick up mirage and make correct sighting difficult.

 

A typical basic ballistic chart for a .22-250 Remington using a JLK 65gn VLD projectile, B.C .397 at 3455fps, is shown in the image above, for field the author carries a copy in a small notebook. The chart is only as accurate as the initial figures you feed into the computer program or application.

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You could use such a chart, and the author has, in conjunction with an electronic rangefinder but another method of sighting had by now appeared and offered another solution.

 

This method relies on a vertical graticule or dot system, the best known, MIL-Dots. You can read how it was developed elsewhere, suffice to say that for our purposes the value of a MIL-Dot is 3.6" at 100 yards.

 

Usually the MIL-Dots are spaced on both the vertical axis for range and on the horizontal axis for wind correction. Using the data mentioned in the above paragraph we can construct an accurate ballistic chart.

  

You can use MIL-Dots in two separate ways. If you know the size of the object (height) you are looking at it is possible to calculate the distance using the formula, size in yards x 1000 divided by the size of the object in MILs.

 

The problem with this type of calculation is that when we are dealing with animals the size of course, varies. However it is possible to use an average which will be better than nothing at all. For example, where we normally shoot pigs, the average animal is about 20 inches high at the shoulder.

 

Examples of MIL-Dot reticles.

 

Thus 20/36=0.55 yards, if the animal is .75 of a millimetre in size the calculation shows that the animal is 412.5 yards away. Because of using an average size the calculation is not perfect but is better than nothing at all.

 

However there is another way of using the information supplied by a MIL-Dot reticule in conjunction with a normal electronic range finder. Knowing the distances between the dots used in conjunction with Load from a Disc (Discontinued, see note below) it is easy to construct a table.

 

Note: Modern ballistic applications such as Strelok and Shooter - Ballistics Calculator can be installed on your Smart phone and/or mobile device. 

 

We normally varmint at long range with a spotter, he ranges the target, the trigger man consults the table and aims accordingly, suffice to say that the “system” is workable and accurate.

 

Of course it did not take long for other sight manufacturers to develop similar systems of hash marks on both the vertical and lateral axis of the traditional cross hairs.

 

LEFT: Ballistic chart compiled using MIL-Dots and ballistic program, very accurate. RIGHT: Ballistic chart using alternative MOA hash marks.

 

Instead of using MIL-Dots some manufacturers use Minute of Angle (MOA) marks, this is in my opinion slightly more accurate as they are closer together than the MIL-Dots and thus do not require as much interpretation between hash marks.

 

Such a reticule is used on the Athlon Argos 6-24x50 sight mounted on my 7mm Remington Magnum for shooting pigs at longer range.

 

A word of warning, some manufacturers have released sights with “MIL-Dots” that are of the incorrect value. One such sight obviously made in the far-east somewhere advertised MIL-Dots but the actual distance between the dots was only 2” instead of 3.6”.

 

Oddly enough aside from this discrepancy the sight in all other aspects is very good and I continue to use it.

 

There is one other little trick that is worth mentioning; at longer ranges you tend with most telescopic sights to have the sight picture at the bottom of the available area.

 

To overcome this, we have found it useful to zero the sight in either one MIL-Dot or perhaps 2/3 MOA above the centre cross hair. This “centres” the rest of the MIL-Dots or hash marks much better.

 

For long range work it is necessary to have a telescopic sight that can accommodate your requirements in relation the animal you seek and the expected range. Furthermore, some sights are much better than others in low light situations, it really depends on individual requirements.

 

Shoot safe.

 

Matthew

 

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