Parallax adjustment with a side focus

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Traditionally, rifle scopes had a fixed parallax set at 100 meters or 100 yards; however, with the advance of shooting sports, such an approach was not adequate anymore. Scopes with fixed parallax offered the best resolution only at one distance (100 meters/yards) at which the target was in focus. At all other distances, the picture was less sharp or even blurry. An even bigger problem with this type of scope was the fact that, when shooting at the target, not at the same distance as the scope parallax setting, the shooter had to be very careful about his eye alignment with the optical axis. If the eye is moved away from the optical axis, the reticle on the target will move, which will worsen the accuracy. Since these errors are small, the fixed parallax option is still considered accurate enough for traditional hunting. For sport shooting, though, such small error leads to poor results. Parallax errors become more pronounced with magnifications higher than 12x, and that means the majority of scopes with magnification range under this value need no parallax adjustment.

With the ability of parallax adjustment, the accuracy of the riflescope is greatly enhanced at all distances. The shooter, however, has to adjust the parallax setting before making the first shot. Such scopes usually have AO – Adjustable Objective or SF – Side focus acronym in their name.

With SF – Side focus scopes, parallax is adjusted with a rotation of the turret on left side of the main tube. Such an approach offers easy adjustment of the parallax in the prone position and is the best solution for situations when parallax must be adjusted often. Due to this reason, such scopes are usually used on tactical scopes and similar, where parallax is adjusted before each shot and distances to the targets change rapidly. Scopes, which offer parallax adjustment with a side focus, are usually bigger and heavier than counterparts with parallax adjustment on Adjustable Objective. They are also more expensive to produce. Due to the size of the internal mechanism for side focus adjustment, the majority of such scopes have a tube diameter of 30mm or more.

The easiest way to correctly set the parallax is to look at the target and gently rotate the ring on the side focus. When the target is in focus and the image offers the best sharpness, move the eye from the optical axis to any direction. If the rifle is properly supported and fixed, the reticle should not move on the target when the eye is moved from the optical axis. If it does, parallax adjustment must be fine-tuned until the reticle is still, even if the eye of the shooter is moving around the optical axis.

Do not mind the meters or yards written on the adjustable objective, since they only provide an approximate value. There is nothing unusual if these values do not correspond well with the actual target distances.

Video presentation of Parallax adjustment on the objective bell

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General features

As the name suggests, these riflescopes are incredibly compact, measuring up to 33 centimeters in length. They weigh below 1000 grams and have a lens diameter of somewhere between 32 and 50 mm.

As these fall into this category, they are equipped with tactical turrets and an FFP reticle (there are some exceptions). Commonly, they feature a MIL/MIL configuration. Even though these riflescopes are small and light, they are packed with tactical capabilities.

Models of firearms compact tactical riflescopes are mounted on

This type of riflescopes are often paired with two distinct groups of rifles:

Semi-auto rifles, chambered in .308 Win., 6.5 Creedmoor or similar
Light tactical bolt action rifles, chambered in .308 Win., 6.5 Creedmoor or similar

It is important to keep the weight at a minimum, which is why these rifles are compact and light. With such rifles, one can expect to shoot at a medium range. Shooting beyond 1000 meters is rare.

Even though riflescopes designed for these rifles fall into the same category, they are not all the same. There are two major groups that we will discuss below.

Compact tactical riflescopes for semi-auto rifles, chambered in .308 Win. or related products

Certain optical devices in this category are designed with the DMR field of use in mind. DMR stands for Designated Marksman Rifle. Unlike sniper rifles, DMRs are almost always semi-automatic rifles with a high rate of fire. A designated marksman (DM) usually covers a distance of 50–800 m. Several riflescopes in this category are designed with the DM's objectives in mind. A wide field of view is important since engaging targets at a close range is common. Since this type of shooting takes place during the day, having a daytime bright illumination is a must. Some are partially designed for the tactical concept called CQB (Close-Quarters Battle) – the lowest magnification of such riflescopes is often 2x or even lower. Some devices feature an adjustable parallax, others do not. It is not uncommon for a shooter to use a compact-tactical riflescope both on a semi-auto rifle chambered in .308 Win. and on an AR-type rifle chambered in .223. Even though not a rule, a MIL/MIL configuration is popular. FFP reticles are much more common than SFP ones.

Compact tactical riflescopes for tactical bolt action rifles

Some optics in this category are designed for certain light bolt-action rifles, predominantly chambered in .308 Win. or 6.5 Creedmoor and packed with tactical features (Remington 700 Police is a great example of such a rifle). The size is the most important factor – only a compact rifle does justice to a compact riflescope. These devices are heavier than the ones for semi-auto rifles but don't exceed the 1 kg mark. With a magnification up to 20x and a lens diameter no bigger than 50 mm, once can pull off a shot up to 1000 m of distance. These rifles can also be paired with full-size tactical riflescopes, but the priority of owning a light tactical rifle is keeping the weight of its accessories at a minimum. Having an illuminated reticle is important, but a weak illumination will do just fine. As the maximum magnification is 12x or higher, one can expect to have an adjustable parallax on such a device. Having lots of elevation range at disposal is crucial, so the riflescope's tube measures at least 30 mm in diameter. The majority of these optics are of the MIL/MIL configuration.

Weight of compact tactical scopes

Weight is an especially important factor for a semi-auto rifle – it has to be as light as possible. Riflescopes for bolt-action rifles can weigh as much as 1 kg. It is important to note that a compact size does not necessarily imply a low weight.

A short presentation of this type of tactical products is available here.

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Short Presentation | Compact Tactical Riflescopes | Optics Trade from Optics-Trade

Parallax adjustment with a side focus

VIDEO