A rifle scope is an invaluable optical sighting device using telescopic lenses, designed to help the user aim accurately with a rifle. There are clear advantages to using a rifle scope rather than lining up iron sights on the target:

• Simplicity. It is not easy to line up a rifle’s front and back iron sights, both with each other and the target. Lining up the scope’s crosshairs (the reticle) with a magnified target is far simpler.

• Magnification and Accuracy. The use of a properly sighted rifle scope allows far greater precision when firing at a magnified target, whether in competition or hunting or stalking. This is particularly important when shooting an animal where it is important to make a clean kill.

• Adjustable Ocular. The ocular can be matched to the user’s eyesight, allowing a clear, crisp image of the target.

Choosing the Right Rifle Scope

It is important to choose the right scope for the rifle. The first step is to limit the choices to the rifle to be used. Scopes designed for a handgun or shotgun will not provide optimum accuracy on a rifle.

The vast range of styles, features and magnification all have specific uses in certain situations, so it is vital to know the uses to which the rifle and scope will be put before selecting the scope.

Key Considerations when Choosing a Rifle Scope

• Level of magnification
• Field of View (FOV)
• Eye relief distance
• Objective lens diameter
• Reticle
• Parallax Adjustable/ Adjustable Objective
• Seal and Coating
• Repeatability
• Tube diameter, length and weight
• Light Transmission
• Exit Pupil
• Quality

These factors are covered in depth below.

Rifle Scope: Magnification

Magnification measures the number of times more closely an object can be seen through the scope than with the naked eye. A 10x magnification means that an object appears 10 times closer, so an object 100 metres away will be visible as though it was just 10 metres away.

Magnification can be fixed or variable. When using variable magnification, it is generally advisable to start with a lower magnification, as, with a close shot, too high a magnification makes causes too small a field of view and reduces light.

Magnification	Benefit	Disadvantage
Variable magnification, such as 3-9x and so on	Versatile enough to cover a range of terrains, distances and light or weather conditions	Less reliable than fixed magnification
Fixed (straight power) magnification, such as 3x, 4x and so on	Generally more reliable Simpler to use – for example a .22 rifle with 4x fixed magnification scope is ideal for squirrels or rabbits	Use limited to one type of shot, so no flexibility for distant or close range

Rifle Scope: Field of View (FOV)

FOV is the area seen through the scope from right to left at 100m. Generally speaking, a wider field of view provides a better result. FOV varies according to magnification, and lessens as magnification increases and vice versa. For example, a 3-9x variable scope (ideal for stalking or hunting) may have a FOV of over 10m at 3x; at 9x, the FOV would be lessened to less than 5m.

Rifle Scope: Objective Lens Diameter

The size of the objective diameter determines the amount of light that can enter the scope and the efficiency of light transmission.

The larger the diameter, the more light passes through the scope, which is helpful in dim or gloomy conditions. Whether choosing a small objective diameter such as a 32mm, mid-range such as 40mm – 44mm or a larger scope of 50mm or more, there are, as ever, advantages and disadvantages. It is sensible to choose the largest objective diameter that can be managed from a weight point of view. A 32mm to 40mm will generally let through enough light for most purposes.

Scope Size	Advantages	Disadvantages
32mm	Lightweight Closer to bore of rifle for greater comfort and stability	Less light able to pass through, so unsuitable for dusk or dawn
40-44 mm	Standard on a medium variable scope, with more light passing through Relatively close to bore of rifle	Starting to get a little heavy
50mm- 75mm	In theory, more light passes through, for clarity of vision and longer shooting days.	Heavy and unwieldy to carry Very high mounting, with effect that just the chin can actually touch the stock making shooting less comfortable Eye alignment through centre of scope is trickier and less consistent particularly when speed is required

Rifle Scope: Reticle

The reticle is used to aim the rifle. There is an increasing range of styles available, and the choice is largely a matter of personal preference. The reticle also helps the user estimate:

• Range or distance
• Wind range

The most common reticle is the crosshair, which can be fine or thick.

Crosshair	Subtention	Advantage	Disadvantage
Fine	Minimum	Precision adjustments for extreme accuracy Ideal for target guns and paper targets	Almost invisible against a busy background or in low light
Thick	Maximum	Show up strongly against foliage and woodland Useful in low light conditions Draws eye towards the centre of the field of view	Less precise

As a result, there is a range of crosshair types available on the market, those most often used are summarised in the chart below.

Type of Reticle	Description	Advantage
Duplex	Cross-hairs that are thick towards the perimeter, and thin out in the centre. Generally made from tough, durable wire which is flattened close to perimeter for greater thickness	Thick bars are easy to see, thin central bars allow for aiming precision Thin central bars can aid evaluation of distance / range
Mil-Dot	Similar to duplex, but includes mil dots (mil = milliradian, a unit of measurement for angles) in the centre to assist with range / distance evaluation For accuracy, almost all mildot calculations need to be made with scopes at their highest power.	All the benefits of duplex, with enhanced ability to evaluate distance / range
Etched	Etched glass reticles allow increased flexibility to include additional shapes such as circles and dots. These benefits outweigh the issues of reduced durability compared to wire, and some light loss caused by glass reflecting light	The additional shapes allow more accurate tools for range estimates and compensation requirements for bullet drop and drift
Illuminated	Reticles can be illuminated by battery powered LED, or plastic or fibre optic light pipes, or tritium which requires no battery	Makes the reticle more visible in low light and overcast conditions, though some of the top-end scopes like Swarovski are clear enough, even in low light, not to need an illuminated reticle.

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Rifle Scope: Parallax Adjustable

Parallax adjustment allows a more precise focus at very high magnification on very distant targets. It is important when shooting at distances greater than 100 - 150 metres, especially with very high magnification scopes such as 10x or more when even slight sighting errors can be significant. Parallax adjustments are usually found on the objective of the scope, though some of the more expensive models now include a side focus which is more practical as it is easier to work with.

Rifle Scope: Turret Adjustments

Turret adjustment is essential for accurate targeting particularly in competition. It is the target turrets which move the cross-hairs in a scope. The turret housing is situated in the middle of the scope tube. The majority of scopes are made with ¼ MOA (minutes of angle) turrets, which are good all-round turrets for most common shooting activity, though 1/8 MOA is ideal for smaller targets which need more precise adjustment. 100 metres is ideal for sighting a scope. If the aim is one inch too low at 100 metres, a scope with ¼ MOA will need to be adjusted 4 clicks in the direction of the “up” arrow on the turret.

Turrets are less useful in an environment where they may get snagged on bushes or knocked in woodland, so hunting scopes do not use turrets.

Rifle Scope: Tube Diameter, Length and Weight

Tube diameter, length and weight of the scope impact both portability and efficiency. A 1" tube diameter is versatile enough for most situations. Scopes with 30mm tube diameters are stronger and allow more adjustment with the turrets, which is useful when using high magnification or shooting long distances.

Length and weight are important to those wanting a low rifle weight. Buying a lightweight rifle is pointless if the scope is heavy. It is possible to buy a lightweight scope as light as 227 grams, though the average weight tends towards 340 – to 397 grams.

Rifle Scope: Light Transmission

Light transmission is the % measurement of total light that can pass through the scope. Only very best scopes can achieve more than 95%, with the majority achieving around 90%, subject to magnification and the size of the objective lens.

Good light transmission makes it possible to shoot through dusk, and provides a brighter, clearer image even in bright conditions, making focus and targeting easier and more comfortable. Poor light transmission provides a foggier image, particularly when losing daylight or at high levels of magnification.

Rifle Scope: Eye Relief Distance

Eye relief is the distance from the eye to the ocular lens (lens closest to the eye) when the entire field of view is visible through the scope. It varies according to the scope’s power. Low powered scopes will have a larger distance, high powered scopes can be very critical not only in terms of the distance of the eye, but also in terms of getting the eye centred through the centre of the tube. It is rare to have eye relief greater than 12cm, and most scopes are between 70 and 90cm.

It is important to ensure the scope’s eye relief is greater than the rifle’s recoil otherwise the recoil may result in a black eye or unpleasant gash across the eyebrow.

Rifle Scope: Exit Pupil

A larger exit pupil makes the position of the head in relation to the scope less critical for accurate targeting.

• The exit pupil is calculated by dividing the objective diameter by the level of magnification:
• 10x magnification on a 40mm objective diameter equates to an exit pupil of 4mm
• 5x magnification on a 40mm objective diameter equates to an exit pupil of 8mm.

It is worth noting that

• 2-3mm is generally enough for normal daylight.
• 5mm minimum is helpful in low light.

Rifle Scope: Lens Coatings

A scope should always be sealed against fog and water, and most rifle scopes have coated lenses to:

• reduce glare
• improve light transmission
• sharpen contrast

The quality of the lens glass and coating is more important than the number of coatings:

• Coated - single coating on at least one lens surface.
• Fully Coated - single coating on all external glass surfaces.
• Multi-coated - multiple coatings on at least one lens surface.
• Fully Multi-coated - multiple layers on external glass surfaces.

A high quality lens with high quality single coating should perform far better than an inexpensive scope with multi-coated lenses.

Rifle Scope: Repeatability

Repeatability is the ability of a scope to shoot with accuracy multiple times without need of adjustment. It is also important to consider how quickly the scope will settle after adjustment. A high quality scope will do so immediately. Poorer quality scopes are likely to need “settling in” either by shooting a few times or simply by tapping on the scope.

Rifle Scope Quality

The rifle scope is a vital piece of equipment as it enables the user to see precisely where to place the bullet. A poor quality or unreliable scope can ruin a day’s shooting, so it is always best to spend as much as can be afforded. The lens glass, coating and light transmission are important, and there are some excellent optics from brands such as Swarovski or Schmidt. Though lenses are one example where the more you spend the higher the quality, these brands are top end in terms of price and quality. There are fortunately also some brands that provide excellent value for money for those with lower budgets, such as Simmons.

Where to Buy Rifle Scopes

Armed with the information above on what to look for in a rifle scope, it is worth looking at eBay, which has a wide variety of brands, styles, prices and choices, including some high quality used scopes, and some excellent prices from trustworthy sellers.

To search for rifle scopes, visit the Sporting Goods portal. Alternatively you can use the search box provided to type in specific information for a more refined selection. Visit eBay’s search tips for more advice.