OS31550SF-FFP

  Magnification  :15x——3x
  Effective objective diameter (mm)  :50——29.6
  Exit pupil diameter  (mm)  :3.33——9.4
  Eye relief  (mm) :88.3——92.1
  Field of view Feet@100Y :8.05——40.22
  Diopter adjustment  :-2.3——+2
  Center tube diameter  :30mm    
  Water proof  （Yes/No） :YES    
  Elevation travel  (MOA)  :±50
  Windage travel  (MOA)  :±50
  Click value:1/4    MOA 0.1MRAD
  Parallax Compensation :20Y ～～∞
  Ocular tube diameter  (mm) h :Φ44.5
  Coating :    Fully Multi-Coated
  Length  (mm) :365
  Weight (g) :892
  FFP or SFP: FFP    

The benchmark specification, combining flexibility and precision, is widely used in scenarios such as tactical shooting, outdoor hunting, and competitive sports. Its design incorporates variable magnification, large objective lens light intake, and focal plane optimization technology, making it the preferred equipment for professional users and advanced enthusiasts.
1. Core specification parameters -
Each set of parameters corresponds to a key functional design, directly determining the applicable scenarios and user experience of the sight:
3-15X magnification range: The 3x low magnification provides a wide field of view, suitable for quickly capturing targets at close range (such as sudden encounters in hunting); the 15x high magnification enables detailed zooming at a distance, meeting the precise shooting requirements of 100-800 meters. The 5x zoom ratio allows for magnification switching to cover the full range of near, medium, and far distances.
50mm Objective Lens Diameter: A larger objective lens means stronger light-gathering capability. Coupled with optical coating technology, it can increase the light transmittance to over 90%. Even in low-light environments such as dawn and dusk, it can still maintain clear and sharp target imaging, effectively solving the problem of blurred vision during low-light shooting.
SF (Side Focus) side focusing function: The parallax can be precisely adjusted through the side knob, with an adjustment range typically covering from 10 yards to infinity. It can eliminate imaging shifts at different distances, especially during medium and long-range shooting, significantly improving aiming accuracy.
FFP (First Focal Plane): The differentiation line and the target imaging are located on the same focal plane, scaling synchronously with the magnification. This means that regardless of whether a magnification of 3x or 15x is used, the ranging and ballistic compensation scales of the differentiation line remain accurate, eliminating the need for recalibration. It is particularly suitable for dynamic target tracking and long-range shooting calculations.
II. Core Performance and Technical Advantages
(1) Optical performance: the core guarantee for clear imaging
The sight utilizes Full Multi-Layer Coating (FMC) technology to further reduce light reflection and chromatic aberration. Even in strong light or backlight conditions, it can avoid glare interference and maintain clear edge imaging. By optimizing the lens material and coating combination, it achieves a "distortion-free" imaging effect, allowing target details (such as prey fur and target scale) to be clearly discernible.
(II) Mechanical structure: dual support of durability and precision
Material and craftsmanship of the mirror body: Mainstream products utilize aviation-grade aluminum alloy (6061-T6) with an integrated molding design. After undergoing hard anodizing treatment, it combines lightweight and impact resistance. After rigorous factory testing, it boasts high-strength shockproof capabilities. It is compatible with various models of firearms.
Adjustment system: Tactical sights are often equipped with exposed locking turrets, each scale is clearly perceptible, and locking after adjustment can prevent parameter deviation caused by accidental touch; the turret design with protective cover balances protection and practicality.
Environmental adaptability: Anti-fog performance is achieved through nitrogen filling, coupled with an IPX7 waterproof design, allowing it to withstand rainy, humid, or dusty environments. It can be immersed in water up to 1 meter deep for 30 minutes without damage. Nitrogen sealing prevents internal fogging caused by temperature changes.
(III) Humanized design: Enhancing operational convenience
Field of view and exit pupil distance: At magnifications of 3-15X, the field of view is typically between 7.2-37.5 feet/100 yards (approximately 2.4-12.5 meters/100 meters), with a constant exit pupil distance of around 4 inches (100mm), which can accommodate different shooting positions and allow for a complete field of view even when wearing goggles.
Differentiation and Illumination: Etched glass differentiation lines exhibit far superior durability compared to printed ones. Certain models feature multi-level red light illumination, which can be activated at night or in low-light environments. Additionally, the central light point illumination design ensures that the target is not obscured from view.
III. Applicable Scenarios
Professional Tactics / Competition: Suitable for long-range shooting and harsh environments.
Outdoor hunting: The lightweight design is more suitable for wilderness scenarios, and the side-focusing function can handle prey at different distances.