Riflescopes & Ballistics Part Two
I n last month’s column, I recommended zeroing your long-range hunting rifle one inch (or one MOA) high at 100 yards. For practical purposes, “one MOA” (MOA being approximately 1.04 inches at 100 yards) and “one inch per 100 yards” are very similar terms, but not quite the same.
Having established that this zero makes sense inside 200 yards, let’s look at how it works at longer ranges. The secret is in two parts. First, you need to understand the bullet’s trajectory. Second, you need a reticle that is more advanced (and more complex) than a simple crosshair.
The first part of the secret is understanding trajectory. When a bullet leaves the rifle’s muzzle, it immediately begins decelerating because of air resistance. At the same time gravity begins tugging it downward at a constant rate. As a result the bullet’s path is a downward arc that gets steeper as the bullet slows down.
To illustrate this, I’ll use Ballistic ExplorerTM by Oehler Research of Austin, Texas to calculate the trajectory of a typical .300 Winchester Magnum load using a 165-grain bullet with a muzzle velocity of 3,100 fps.
Because atmospheric data influences how much air resistance the bullet encounters, this example is at sea level with temperature of 59º F and a barometric pressure of 29.56 inches of mercury. If you are hunting at a higher altitude, higher or lower temperature and barometric pressure will affect trajectory in a predictable way that you can enter into Oehler’s Ballistic ExplorerTM or other ballistics program. Tape this data onto your rifle’s buttstock for reference in the field.
If this seems extremely technical, that’s because it is. The important thing is that trajectory can be predicted well enough to provide you with a fairly accurate long-range shooting solution. Or, you could avoid all this and limit yourself to shots closer than about 200 yards. It’s another case of “Ya pays yer money and takes yer choice.”
Assuming that the rifle is zeroed one inch high at 100 yards, the bullet will strike a tad less than an inch low at 200 yards. At 300 yards, the bullet will be 7.25 inches low. At 400 yards, it will be 19.5 inches low; at 500 yards, 38.25 inches low. At 600 yards, the bullet has dropped about 65 inches—that’s nearly five and a half feet!
By now the trajectory arc is so steep that in another 100 yards, the bullet has dropped another three feet to more than 100 inches.
Military snipers routinely make killing shots to far greater ranges than this, but remember, they are not concerned with a clean, humane kill. A disabling wound on an enemy soldier is sufficient for military purposes—even preferable.
Being ethical hunters, we strive for a quick, humane kill, ideally with one shot. When you consider wind drift, steady hold factors, accuracy of the rifle, a clean, one-shot kill at these ranges becomes problematic. For this reason, I’ll confine this discussion to distances under 600 yards.
This brings us to the second part of the secret to long-range shooting while using a one-inch-high zero at 100 yards. I’m sure many of you know what that secret is—a riflescope equipped with a reticle with one or more secondary aiming points below the crosshair intersection.
But if you think I mean a “mil-dot” reticle, you’d be wrong. A mil-dot reticle does offer secondary aiming points, but it is a clumsy solution compared to the Varmint Hunter reticle available in Leupold VX-3 riflescopes and similar reticles from other scope manufacturers.
Instead of dots on the vertical crosshair spaced at a constant 3.6 MOA interval, a ballistic reticle uses a series of secondary horizontal crosshairs spaced at progressively greater intervals that correspond to the steepening bullet path as it travels down range.
As a bonus, these secondary crosshairs usually have a pair of tic marks, one on each side of the vertical crosshair. These tic marks are spaced to compensate for a 90-degree crosswind of 10 mph. Spaced farther out is a dot on each side that offers the hold-off for a 20 mph crosswind.
Used with a decent laser rangefinder, this gives you the range and windage data you need to score on a game animal up to a quarter of a mile and beyond. This assumes you have a steady shooting position and the marksmanship skills to necessary to make the shot.
Let’s see how the Leupold Varmint Hunter reticle works with the .300 Win Mag data discussed above. Remember this data should be pasted to the side of your rifle’s buttstock.
Using a zero of one-inch high at 100 yards, the primary crosshair intersection is zeroed at 180 yards. The first secondary crosshair is 1.81 MOA below the main crosshair intersection, which gives you a longer range zero at 280 yards.
The next crosshair is 4.29 MOA below the main crosshair giving you a 380-yard zero. At 7.02 MOA is the last crosshair, which marks a 485-yard zero. Below that is the bottom post at 9.72 MOA and a 570 yard zero.
You probably notice that these downrange zeroes are not in 100-yard increments. That’s because each cartridge/rifle combination has a slightly different trajectory. This trajectory is for the .300 Win Mag with a 165-grain bullet at sea level. This same load will shoot a bit flatter as altitude increases. Also, a higher temperature will flatten the trajectory, and a lower temperature will make it steeper.
All these changes can be entered into Ballistic ExplorerTM and give you a decent firing solution for the temperature and altitude where you plan to hunt.
Don’t forget, you also have to think about wind drift at long range, but the Varmint Hunter reticle gives you the necessary aiming point to hold into the wind, assuming it is a direct crosswind. You do have a wind meter, don’t you?
A quartering crosswind will require a half-value hold-off—assuming it’s constant all the way to the target. A “fish-tailing” wind is a “whole ’nother” thing to complicate your life.
By now, if you count the number of times I mentioned the word “assuming,” you should be ready to chuck the whole idea of long-range shooting. Yet, there is something enticing about the idea of plunking a round into the next zip code and placing it right where it needs to go. I feel it, and I’ll bet you do, too.
—by Stan Skinner
Meopta MeoTac ZD 1-4x22RD
My optic recommendation for defensive-styled, multipurpose rifles recently has been a low powered illuminated scope. For several years I have fulfilled this for 3 Gun and hunting using the Meopta MeoTac ZD 1-4x.
While I do normally prefer a non-magnified red dot for speed shooting inside 100 yards, true 1x magnified and illuminated optics such as the Meopta ZD give you that same advantage with the option of zooming closer to 4x with the slide of a lever.
The Czechoslovakian manufactured optic boasts a very clear and high quality glass on par with other high-end scopes retailing in the $2,000-plus range. Meopta has been slowly entering the US market, modifying their adjustments and reticles to match the aiming systems we Americans prefer.
One of the great advantages of the MeoTac scope is the illuminated, red dot Ballistic Drop Compensation (BDC) reticle. This has been my go-to optic for 3 Gun competitions for this primary reason. It has a two-MOA illuminated dot in the center with two, nine-MOA horizontal lines for quick target acquisition.
For the farther targets three chevrons are spaced out to use for holds out to 500 yards. I’ve had competitions where you engage rifle targets at five feet to 500 yards in the same stage, and this reticle made it all the easier.
On low magnification there is a very slight “fisheye” when viewing with both eyes open. But I’ve seen more lens shift in other manufacturers 1x red dots. I added a throw lever for faster adjustment of the magnification ring.
The illuminated reticle is absolutely necessary when shooting in bright light. The second focal plane, etched glass reticle is too fine to pick up without it glowing bright red. However, at least it is there in case the electronics fail.
Adjusting the knob on the left side of the optic activates the reticle illumination between its seven brightness positions. I usually run my illumination on positions five to seven depending on the brightness and distance. The lower levels are great for night shooting.
The MeoTac uses standard 2032 batteries. There is no “time out” shutdown feature and battery life is only rated for 120 hours, so I would recommend keeping a few spares ready in case you inadvertently leave it on and drain the battery.
The turrets adjust your point of impact ½-inch per click at 100 yards and seem to be spot on. You must remove the large turret caps for any adjustments. They are tied onto the optic with a small string so you don’t misplace them. I have seen a slight issue with the rubber o-rings that the turret caps snug up against. They distort if over-tightened, so make sure you don’t torque down too much.
I found the MeoTac listed around $1,100. It might seem like a lot for a red dot, but for a dual-purpose high quality European magnified scope that’s built with German Schott glass, it can be considered quite a deal.
—by Dustin Ellerman
Email Dustin Ellermann at ContactUs@fishgame.com