Quick Answer
A variable optic on an AR should have a 1-4x power range, a 30mm objective lens, and a first focal plane reticle to ensure accurate ranging and shot placement at varying distances.
Reticle Features
When choosing a reticle for your variable optic, consider one with a 1 MOA dot size and a 5:1 or 10:1 subtension ratio. This will allow for precise shots at longer ranges. The reticle should also have a BDC (Bullet Drop Compensation) curve or a trajectory map to account for bullet drop and wind deflection.
Objective Lens Size
A 30mm objective lens is the minimum size recommended for accurate ranging and shot placement at longer distances. This size lens will provide enough light gathering to illuminate the reticle clearly, even in low-light conditions. Larger objective lenses (such as 36mm or 40mm) are available but may add unnecessary weight and cost to the optic.
First Focal Plane (FFP) Optics
First focal plane (FFP) optics are essential for accurate ranging and shot placement at varying distances. In an FFP optic, the reticle is located in the first focal plane, which means that the reticle’s size and subtension ratio remain consistent at all power settings. This allows for precise calculations of bullet drop and wind deflection, even at higher magnification settings.
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