A biathlon rear sight is more than just one part. It starts as a base unit, but can be adjusted and extended through a handful of interchangeable pieces that let each athlete create the exact sight picture they need.
Understanding how each of these pieces works within the system is important in evaluating what benefit they have to your position and shooting preferences.
The goal of this article is to broadly review each of the components in a biathlon rear sight system, examine how they work and what role they play for you.
1. The Diopter
The diopter is the largest, most recognizable piece of the rear sight. Its movement is what allows biathletes to adapt their rifles to changes in elevation, light, and wind.
Biathlon diopters have three important components:
- Windage & elevation adjustment. Adjusting these knobs, by 'clicks', will shift the position of the rear sight block within the diopter, changing the bullet landing location when the rear and front sights are aligned. For Gehmann 590-B, and Anschütz 6827 rear sights, one 'click' of either adjustment knob will shift the bullet placement by approximately 3 mm.
- Snow cover. Essential to any biathlon rear sight to prevent ice build up in cold conditions, or keep out rain during the summer months. Protecting the inner workings of the diopter is also important for its longevity.
- Clamping rail for 11 mm Anschütz dovetail. Anschütz rifles dominate the choice of biathletes worldwide for good reason with their remarkable performance. The diopter is mounted to the rear rail on these rifles, and must be compatible with the 11 mm standard.
Diopters are robust pieces of equipment, but can be disrupted with neglect or use over time. Those which cannot shift accurately, or repeatedly, should be serviced as soon as possible or replaced. The foundation of accurate shooting requires a reliable diopter.
The Gehmann 590-B, without rear aperture attached.
2. The Aperture / Iris
To be used properly a diopter requires an aperture, or iris, to be threaded into it. Apertures are what the eye looks through in order to create a sight picture.
Apertures may vary in size and length, but should retain a standard viewport diameter (the pin sized hole) of 1.2 mm. They may include a clamp ring, making it simple to attach a blinder or eye cup for protection against light.
Specialized options, such as the Gehmann 510 Rear Iris, is an adjustable iris with a 0.5 to 3.0 mm range, controlling the size of the aperture opening. A smaller opening sharpens focus on the target; a larger one lets in more light. For advanced athletes competing in multiple locations, this can be beneficial to adjust to different ranges and weather conditions.
A standard length aperture (left), and compatible clamp ring (right).
4. Aperture Extensions
For smaller athletes, instances may occur where the rear sight does not extend far enough back to reach the eye for a proper position.
To solve these situations, a Rear Sight Iris Extension can be used to increase the distance that the aperture extends out of the diopter. By threading the aperture into the extension piece, and in turn threading the now longer aperture into the diopter, an additional range of 10 mm can be gained.
By making sure the aperture reaches the eye without an athlete straining their neck, a
5. Riser Sets
Similar to the aperture extension solving sizing issues for smaller athletes, riser sets can solve issues for larger athletes.
Riser sets raise the entire rear sight assembly to match your stock and cheek position.
Athletes with larger frames may require a rear sight that sits higher off the rifle in order to maintain a comfortable neck and cheek position.
Please note, the amount the rear sight is raised should be matched in the front sight to a near identical amount. Height differences between the two that are greater than 2 mm may restrict the vertical movement of the diopter. Attention should be given to ensuring these dimensions are always equal.
A 16 mm rear sight riser, and 16 mm front sight pillars for equivalent rising.
6. Blinders
To block light from entering the eye, a blinder can be attached to the rear aperture or the diopter directly. Ensuring the ability to make a clear sight picture through varying conditions can be exceptionally beneficial for shooting performance, especially for inexperienced athletes that require reduced distractions.
Blinders may be fashioned out of many materials, with the most common made from foam, or rubber. Good performing blinders are not rigid, or prone to folding as they create issues of reforming each time an athlete must shoot.
Preformed, silicone models, such as the Larsen Ambidextrous Blinder, have the benefit of this flexibility while not bending out of shape.
For more experienced athletes, blinders can be disadvantageous as depending on their size they may block valuable range information, such as light or wind shifts.
What's Left to Know
On the surface, a biathlon rear sight may look quite busy, but its operation and requirements are very straightforward. Above all, it needs to be reliable in order for an athlete to have the confidence in their equipment.
These components are designed to be mixed and matched rather than replaced as a full set. If you're unsure which combination fits your position and size, please contact us.