1st and 2nd Focal Plane Rifle Scopes and their differences
2nd focal plane rifle scopes are what most of us are used to using and have been around for some time. With variable magnification rifle scopes, the shooter can zoom in and zoom out on the target. When doing so on a 2nd focal plane scope, the reticle is always the same size as shown below.
As you can see from the above left image when zoomed in, holding off 4 Mil Dots above the 1″ center bulls-eye places the cross-hairs 1″ high. When zoomed out as on the right side image one sees the center cross-hair is now approximately 1-3/4″ high. This is why it’s critical to always shoot at the same magnification that you set up your hold over chart at.
It is possible to use a 2nd focal plane scope and shoot at different magnification, one just needs to do a little math to calculate the difference in hold over caused by the change in magnification, but who want’s to do math.
With a 1st focal plane rifle scope, the reticle will increase in size as magnification is increased, and decrease in size as the shooter zooms out from the target as shown below.
From the image above, you can see that regardless of being zoomed in or zoomed out, a 4 Mil Dot hold over always places the center cross-hair 1″ above the bulls-eye. Now the shooter is free to choose what ever magnification to shoot at with no effects on the point of impact.
The drawback to 1st focal plane rifle scopes is that they are difficult to manufacture, components need to be paired correctly and assembly time can increase 3 to 4 times making these scope more expensive.
There is an option to holding over using the reticle and that is to adjust the elevation turret to the distance and always use the center cross-hairs. In essence, the shooter is re-zeroing the scope to compensate for the projectile drop. In this case, magnification has no effect either as shown below.
Another advantage to adjusting the elevation turret to the distance is the shooter now has easy visual reference to the windage horizontal markings. The downside to clicking the elevation turret, first you’ll need a scope with raised turrets that are easily turned. The second downside is you may need to spin the elevation turret around more than once. This may not seem an issue but when you want to return the elevation turret to it’s original position you’ll need to remember if you went 2 revolutions or 3. It’s easy to get lost especially if you put your rifle away for the day and come back a week later.
This where the MTC Optics Viper Pro with the Smart range turret excels. The turret is geared and has a customizable window for the shooter to match the scope to the rifle and the projectile.
For more information and specifications on 1st and 2nd focal plane scopes as well as the MTC Viper Pro, visit out Optics selection.