Good optics are imperative to ensure repeatable results at long range. We are not going to compare brands here but point out desirable features and explain why they are needed.
The old adage, “You can’t hit what you can’t see”is definitely applicable. That does not mean you need 30 times magnification to ensure repeated hits on a steel plate at 1 000m. A scope somewhere between a 4–12x40mm and 8–32x50mm is entirely sufficient. In fact, a magnification of 30 will adversely affect your target acquisition in several ways. The field of view is reduced to such an extent that you will struggle to identify changes in wind strength and direction, and locating the target can take longer than necessary, especially a moving target. Image quality starts to suffer with high magnification, and the shooter has limited view of non-targets entering the sight picture unexpectedly. Also, most scopes have a reduced eye relief at the higher end of their magnification range.
Moreover, on days with heavy mirage, high magnification will affect the sharpness and location of the image as the target will flutter around erratically. Typically, high magnification of 20x and above is usable only until about 11:00 and after 15:00, due to light angle, mirage and haze. Lastly, you will have difficulty seeing your bullet trace as the narrow field of view will limit your sighting of the bullet to a very brief arc as it reaches the target. However, high magnification does help to check for hits on steel when providing a good quality image.
It is crucially important to choose a scope with a reticle that matches the turrets. A mildot reticle must have turrets adjustable in increments of mils. The same goes for MOA systems. A matching reticle/turret system enables you to use the reticle to measure the distance of bullet impact off target and directly apply this data to your turret adjustments without making any calculations.
When using the reticle for ranging, the mil scales are easier to calculate. In reality, the difference is that 1 mil equals 3.6 inches at 100yds (1 mil is 10cm at 100m), while 1MOA is 1.047 inches at 100 yards. Notwithstanding this difference, on the same scope design, MOA and mil will have the same maximum adjustment.
Consistency and repeatability in turret adjustment is more important than image quality. The precision of the reticle’s movement with each click, and the consistency of this movement under field conditions, is of crucial importance in a long-range scope. Without this, achieving a hit for every shot at varying distances, by simply dialing in with the turrets, is not possible.
Reticles have come a long way since the duplex or simple post and cross-wire of the earlier scopes. If you are dialing turrets for all your shots and you are never under pressure to shoot quickly, then a duplex-type will probably meet your needs.
All scope tubes have a smaller tube inside them that houses the erector lens system (which, among other things, reverts the inverted image). In a fixed-power scope, the erector lenses are permanently fixed in place in this inner tube. In a variable, the erector lenses move in relation to each other within the erector tube as you adjust the magnification. The image gets bigger or smaller as the distance between the erector lenses varies. Variable scopes come in two basic designs: those with the reticle in the first focal plane (FFP) and those with the reticle in the second focal plane (SFP). This means that FFP reticles are positioned between the objective (front) lens and the erector lens system, whereas SFP reticles are positioned behind the erector lens system (nearest the ocular lens). In FFP scopes, the reticle is magnified along with the image as you adjust the magnification, thus becoming coarser as the magnification increases. In SFP scopes, the reticle remains the same size/thickness irrespective of the changing image size as magnification is increased or decreased.
Read the full article in the December 2018 issue of Magnum