December 07, 2017
With the advent of the scope came the desire to get the most out of it. This article explains options on how to better use each reticle. Each reticle choice will have its pluses and minuses depending on what you want from a reticle and how you intend to use it.
I'll cover the Duplex, Mil-Dot, ballistic, Horus and TReMoR here.
DUPLEX: SIMPLE, BUT USEFUL
First up is the Duplex. This reticle has been used primarily with the crosshairs zeroed at 100 yards or 100 meters, while some prefer to zero the crosshair at 200 or 300 yards/meters. Most shooters tend to zero at 100 yards, so we'll use that as our control.
It's possible to use this reticle for range estimation (milling) and turn it into a ballistic reticle. To begin, we have to understand what the measurements are to which the reticle is equal. To do this, place a target at 100 yards/meters. Then, measure from Duplex to Duplex either with a measuring instrument or by marking the target, then, using a mil reticle, overlay the marks to find what the Duplex to Duplex distance would actually mil.
Let's say that from Duplex to Duplex measures two mils. I could then zero my rifle at the top Duplex at 100 yards. This would make my crosshairs zeroed at one mil, or close to 273 yards (250 meters). The bottom Duplex is two mils from the 100 zero (at the top Duplex) and equivalent to 417 yards (381 meters). Now we have a basic Duplex reticle that has been turned into a ballistic reticle, and since we found the distance between the top and bottom Duplexes and the crosshairs, we can use this information in a mil-relation formula.
There is another use for the Duplex reticle. If the scope is a second focal plane, we need to find out where half power is. Go back to the target where we measured the distance between the Duplexes. Turn down the power on the scope until the two marks that represent the Duplex-to-Duplex measurement on the target now fit between the crosshair and a Duplex. The magnification ring is now at a true half power.
Not all scopes will be correct at the number that is engraved onto the magnification ring.
When we turn down the scope to half power, we can accurately extend our range. When we turn down the scope to half power, we double (in mils) any measurement we make with the scope.
If the crosshair-to-Duplex distance was one mil at full power, at true half power it equals two mils. In our example above, we zeroed the rifle at 100 yards at the top Duplex, so we really zeroed the crosshair at 250 meters.
When we turn down the power to half power, the crosshairs are still zeroed at 250 meters, but the 100-yard hold would now be halfway between the crosshair and the top Duplex at one mil. This would then make the bottom Duplex equivalent to a three-mil hold from our 100-yard zero. This would be a range of 476 yards (435 meters).
Using the scope at half power now gives us the ability to take a shot, at range, with a more refined aim than just a hold above the target. Another positive use of the Duplex reticle is shooting in low light. The Duplexes help center the crosshairs in low light and also give us the ability to accurately extend our range.
MIL-DOT: LIKE OLD, COMFORTABLE SHOES
The creation of the Mil-Dot came from the pursuit to reach out even farther. The mils allow us to range targets by using a mil-relation formula:
Size of target/mil size of image times 27.778 for yards (or 25.4 for meters)
The Mil-Dot also gives us the ability to use holds in elevation or windage. This will allow the shooter to gain a little speed without the loss of accuracy. This reticle is used in a lot of ways. Most will dial the elevation turret and then use the horizontal mil dots to hold for wind. Some will dial both elevation and wind. I don't recommend this, since it takes away the speed that shooting a hold for wind will give you.
Also, not all turrets track perfectly, so if we are dialing our turret, we may be losing our zero and/or not even accurately dialing the proper amount of mils or MOA into the reticle. These adjustments are historically skewed on a lot of scopes and can never be more accurate than a precise reticle.
In the same way that we discussed how we can get more out of the Duplex reticle, we can also get more out of Mil-Dots. I like to call this one the Poor Man's Horus.
Most of the time we never use the top half of the reticle. If we started by dialing the elevation turret up five mils or as close as we can to 17.2 MOA (these are equivalent), we now place our 100-yard/meter zero at the top Duplex and allow ourselves the use of 10 mils from the top Duplex to the bottom Duplex.
This may present a problem as the wind picks up and one finds himself holding out in space. This is one of the few times that dialing for wind is a good idea. It's less turning of a turret than elevation.
I came up with this idea while training some students and working on the old 500-meter holdover/under drill. As I thought about the drill, it suddenly occurred to me that there was a faster way. Speed was the reason for the 500-meter holdunder/over drill in the first place.
The benefits of the Poor Man's Horus are just common sense. If you know your holds every 100 yards/meters, it's easy to fall into the exact hold without any math, thus making it faster. You should already have these holds memorized and placed on your stock or scope-cap cover.
If we are unfortunate enough to have a scope that's in the second focal plane, we can repeat the process we used with the Duplex reticle to find the true half power. Once we have done this, we can reach out even farther because each Mil-Dot is now worth two mils.
At half power, the 100-yard/meter zero is now 2½ mils above the crosshair, which is now equivalent to five mils. The bottom Duplex is now worth 15 mils. We now also have the knowledge to further utilize the 10-mil mark farther down in your reticle, if you have one, which is now 25 mils at half power.
This reticle has been changed for the better with the advent of the Leupold TMR reticle. The TMR has half-mil subtension as well as .2-mil subtension from the fourth mil to the thick stadia line. This reticle is very useful and has really helped the Mil-Dot. It's easier to mil with and more accurate for range estimation.
BALLISITIC: GOOD, BUT WITH LIMITATIONS
The ballistic reticle would seem to be the reticle that would fix all of our problems. Ballistic reticles work really well if we're not shooting long range. If we only shoot out to 400 or 500 yards, this reticle may be a wise choice. Before purchasing one, it's important to know the variables that come into play to make these reticles work.
For starters, each ballistic reticle, like all ballistic-drop-compensated turrets (BDC), is built around a specific muzzle velocity, ballistic coefficient (BC) and density altitude (DA). This means that the reticle doesn't work if we switch the ammo we're used to using, change the density altitude by changing our elevation or have a big swing in temperature (even at the same elevation).
Some will say that they can effectively correct their reticle by dialing the elevation turret. This does correct the error for that range, but only for that range. The rest of the reticle is now incorrect. Therefore, a correction must be made every time one chooses to shoot at a different range.
What some do not know (or possibly do not want you to know) is that DA also affects how much wind deflection the bullets will have, so the wind lines in a ballistic reticle will have problems being correct with any DA changes.
Example: If we change from an altitude of 2,500 feet to an altitude of 8,000 feet, our elevation hold for an 800-meter shot is less by about one mil, or more than 30 inches. Our 20-mph wind hold is less at 8,000 feet by around the same one mil, or 30 inches. But a shot at 400 meters with the same change in DA only gives us a half-MOA difference in elevation and a little over one-MOA difference for the same wind.
As we can see, ballistic reticles are potentially useful tools for the shooter who doesn't engage long-range targets with any potential DA changes.
HORUS: YEAH, IT'S SCIENCE
Horus reticles are mil based and have .2-mil subtension marks between mils as well as left and right marks for wind holds. The secondary stadia lines below the main crosshair allow for elevation holds out to extreme distances without having to dial a turret. They also give us the ability to have accurate wind holds without dialing.
Second-shot corrections are perfect, as we now only have to drag the point where our first shot hit in our reticle to the target and pull the trigger. This style of reticle has truly changed long-range shooting. When needed, it allows the shooter to dial the elevation turret to use more magnification or just use pure holds. Using holds is always more accurate than dialing.
TReMoR: THE NEW KID
The TReMoR means The Refined Mil Reticle. It has subtensions at .2, .5, .8 and between the 4th and 5th mil lines, and it has mil marks at .2, .5, .6, .7, .8 and .9. This allows the shooter to mil within .1 mil. If a shooter can see accurately to .1 mil, he can extrapolate down to a half tenth. It also has the speed mil shooting formula inside the reticle, but now the shooter only has minimal movement to engage.
The numbers serve two purposes. They not only let us know what mil line we are on, they serve as the mover hold for target speeds of four mph. The newest main feature is the time of flight-based wind dots. If we are shooting a 5.56 NATO round, the dots are three mph. If we are shooting a .308 Win. or .300 Win. Mag., the dots are four mph.
The Horus/Kestrel unit and the Horus Atrag 4.0 version will have a TReMoR option that will tell the value of each dot based off muzzle velocity (MV), ballistic coefficient and density altitude. With a PDA or Kestrel, this reticle is always perfectly calibrated.
This reticle makes shooting in winds very easy and doesn't require the use of wind formulas anymore. Just find the value of the wind in mph and hold that dot. That's it. It is simple to use and has all the capabilities of a mil-based reticle.
So, what's your pleasure? It's your choice, and there are many. But like all things in life, we should never allow ourselves to get caught in a comfort zone. We limit ourselves by not being open to options. We should know how to use every reticle and make the most of each of them.
Don't let others put limitations on you. Long-range shooting is not magic, and it's not that hard. With the right tools, anyone can do it. Embrace the new technology, and enjoy your improved long-range capabilities.