While there is quite a bit going on inside a riflescope’s tube to get you on target and keep you there, the Sightmark Pinnacle’s TMD reticle is designed to help you successfully use holdovers, determine appropriate windage and elevation adjustments, range targets and even acquire zero or sight in.
The Pinnacle’s tactical mil-dash reticle, also known as the TMD reticle, is made of referencing points—including crosshairs, subtensions, subtension or referencing lines, numbers along the vertical and horizontal axis and a grid pattern in the lower half of the reticle some people refer to as a Christmas tree.
Let’s look at each reticle element and learn how they can be useful.
The first and most obvious element of the TMD and most other reticles are the crosshairs. Crosshairs are comprised of the primary vertical and horizontal axis referencing lines that intersect at the reticle’s center point. You may see optics sometimes that consist of only crosshairs. Crosshairs create an initial point of reference for all other referencing information on the reticle and serve as an integral part of the point of aim when sighting-in a firearm or shooting at a distance where a bullet’s trajectory change is negligible. Of course, crosshairs also become the point of aim at greater distances when mechanical windage and elevation adjustments are made, at least until you run out of adjustment—possible even with the Pinnacle when shooting extreme distances.
Subtensions and Subtension Lines
Subtension is the distance a reticle covers at a certain range. Subtensions are the spaces between the subtension lines, also known as referencing lines or hashmarks. Just to the right of the vertical axis line and below the horizontal axis line to the right of center, there are numbers 2, 4 and 6. Each number references the corresponding hashmark’s distance from center. On the Pinnacle 3-18×44, each subtension is 0.5 mil, at least until you reach the top of the vertical and far right of the horizontal axis. The subtension lines for those final 3 mils reference 0.2 mil. These subtensions and hash marks are vital to using holdovers and ranging targets, especially on first-focal-plane optics.
As examples, if you held the reference line on the horizontal axis above 2 on the bullseye, you would be holding 2 mils left—the reticle’s crosshairs are now 2 mils to the left of center mass. If you place the hashmark referenced by the number 4 on the lower half of the vertical axis line on the bullseye, you are now holding over 4 mils. As a final note, if you held between 2 and 4, your holdover would be 3. More finite vertical holdovers in this example might position you at 2.5 or 3.5 mils. The same applies for windage.
Remember, each subtension line is 0.5 mil. Of course, this is only true through all magnification ranges on a first focal plane riflescope. As they relate to second-focal-plane riflescopes, subtensions and subtension lines are only accurate representations of standard mil, or MOA on other scopes at a single power of magnification. This is the primary reason why long-distance shooters prefer first-focal-plane riflescopes like the Pinnacle 3-18×44.
The further we move from the crosshairs, the more difficult it becomes to acquire precise holdovers. Holdover is when you must aim above your intended point of impact to compensate for bullet drop. Since the lion’s share of holdover aiming occurs below the horizontal axis, the Pinnacle’s TMD reticle includes a subtension grid that widens as you move further down the vertical axis. If you were to use 4 up and 2 left as holdovers, you would hold the mark in the grid located 4 mils below the horizontal reticle and 2 mils to the right of the vertical axis on the bullseye.
Subtensions are also great for rapid zeroing or sighting in. For this example, we will use 100 yards as our distance. Shoot the target and note the shot placement. Now, place the crosshairs on the bullseye again and determine how many mils your bullet hole is away from dead center.
If the subtension lines revealed your shot was 2.5 mils below and 2 mils to the right, you would adjust your elevation turret up 25 clicks and left 20 clicks, considering each click is 0.1 mil of adjustment. Take another shot and you should be on the bullseye or left with only fine-tuning. If you’re zeroing, don’t forget to set the Pinnacle’s zero stop now, which guarantees an instant return to the original zero. You can find that video tutorial on Sightmark’s YouTube channel.
Ranging targets using subtensions can be a quick, relatively accurate way to acquire distance data without the use of a laser rangefinder or other technology; of course, to do so really requires a first-focal-plane scope like the Pinnacle 3-18×44 or, perhaps a second-focal-plane scope set on a single power of magnification. Again, the beauty of a first-focal-plane system is that the incremental values represented by subtensions, lines and numbers, never changes at any magnification. Subtensions mean the same at 3 power as they do at 18 power, whether the target is right in front of you or 1,000 yards away.
Windage and Elevation Axis
Remembering the Pinnacle 3-18×44 is based on mils with 0.1 mil turret adjustments helps us understand some quick math. 1/10th mil, most often referred to as 0.1 mil, moves your point of impact 0.36 of an inch at 100 yards. This is equal to 1.8 inches per .5 mil and 3.6 inches at 100 yards per full mil of adjustment. Simplified, because subtension lines on the Pinnacle’s reticle are based on 0.5 and 1 mil increments.
This means a 36-inch tall by 18-inch silhouette would span the vertical height of 10 mils and the horizontal width of 5 mils at 100 yards. So, an adult figure that filled 10 vertical mils and 5 horizontal mils of your reticle, would be an estimated 100 yards away.
Since 0.1 mil at 100 yards is 0.36 of an inch, we know 0.1 mil represents 1.8 inches of adjustment at 500 yards. Extended out from 0.1 mil to a full mil, we then know a full mil represents 18 inches at 500 yards. Since the target is 36 inches tall by 18 inches wide, we know it should fill 1 horizontal mil and 2 vertical mils. If so, that target is 500 yards away.
At 1,000 yards, we can double that. We know 0.1 mil is 3.6 inches of adjustment at 1000 yards and a full mil is 36 inches of adjustment at that range. So, the target we’ve been looking at would fill 0.5 mil on the horizontal axis and 1 mil on the vertical axis. Understanding the adjustment values of 0.1 mil, 0.5 mil and 1 mil at 100 yards and then extending out over yardage, coupled with identifying your target and possessing basic estimation knowledge of its size, means you can range any identifiable target with some degree of accuracy simply by utilizing the subtensions and hash marks in the Pinnacle’s reticle.