What is the difference between first and second focal plane riflescopes?
There are many factors you need to consider when purchasing a new variable-power riflescope. Many shooters only focus on the magnification range and price. A potentially but overlooked factor is the placement of the reticles on the first and second plane. What’s the difference?
First Focal Plane
First focal plane scopes have the reticle placed towards the front of the optic. When the magnification of the scope is increased, the reticle’s size increases with it. In doing so, the reticle remains the same perspective on the target’s size as you increase or decrease magnification. These scopes provide long-range and tactical shooters more accuracy due to the constant MIL/MOA values. It means that the holdovers for the optic are true at all magnifications.
Second Focal Plane
Second focal plane reticles are placed towards the back of the scope. When the magnification of the scope is adjusted, the reticle’s size does not increase. The MIL/MOA values are only correct at one magnification, which is almost always the base magnification. When the scope is adjusted to a different magnification, the spacing changes and is not consistent. A shooter would have to do some math to calculate the actual values of the subtensions at different magnifications.
First focal plane scopes are increasing in popularity with hunters because they are more versatile than second focal plane systems. Whenever you are hunting, you cannot predict the outcome before the hunt. The animal could walk out at 25 yards or 500 yards. Using a first focal plane scope allows hunters to make accurate adjustments, again, because they know the subtension values are consistent throughout the magnification range. Additionally, having a larger reticle means more precise holdover adjustments. Furthermore, if you miss your first shot but see your point of impact, you can place your second shot more accurately.
A first focal plane scope is generally more expensive than a second plane scope, but it can be worth the price difference depending on how you shoot. Being able to adjust your magnification without second-guessing your subtensions can beneficial when shooting longer distances.