September 23, 2010
Here's how to make sense out of ranging and drop-compensating reticles.
This Leupold 6.5-20X has a custom reticle designed for long-range shooting at Coues deer. Today's shooters have terrific options to make accurate long-range shots possible.
A scope reticle used to have a single function: indicate where your bullet would land. Now many reticles are designed to help you estimate range as well. And some scopes are built so the reticle can even compensate for distance.
The simplest rangefinding reticles comprise two horizontal stadia wires. The space between them bracket a specified measure at a given range. Stadia wires might, for example, bracket the 28-inch depth of a bull elk's chest at 200 yards. An elk filling half the space is about 400 yards away. An ordinary plex reticle can help in the same way. Just bracket the target between the intersection and the top of the bottom post. You'll want to check this measure at various distances before season by shooting on paper.
Most variable scopes sold in the U.S. have rear-plane reticles, so target coverage changes as you change power. You'll want to choose one magnification for ranging. Reticles in the front focal plane (popular in Europe) change apparent size as you change power but remain in a constant size relationship with the target. No matter what magnification you choose, bracketing the target will show you the same picture--and indicate the same yardage.
Hunters in the U.S. like the rear-plane reticle because it covers less of the target at high power, for greater precision, and it is easy to see at low power, when you're taking quick aim in thickets. Front-plane reticles become hard to see at low magnification and thick when you crank the power up--just the opposite of what you want.
Scopes sold by Shepherd have two reticles--one in the front focal plane and one in the rear--that are superimposed. The rangefinding (front) reticle has a series of circles that does not interfere with the aiming reticle. You use the circles to corral targets of known size to determine distance.
The rear-plane aiming reticle remains proportioned for accurate shooting at small targets far away. A friend of mine thinks his 6-18X Shepherd an almost unfair advantage. He says, "Coyotes that think they're standing off far enough to be safe really don't have a chance."
The Ballistic Plex introduced by Burris in its Fullfield II scopes is both a rangefinding and range-compensating device. The thin wire beneath the center of the plex reticle has three short horizontal hash marks, each gap incrementally bigger than the one above it. The differential spacing of the tics reflects the parabolic arc of your bullet.
Zero at 100 yards with a 180-grain .308 bullet and you'll hit at the first hash mark (three inches low) at 200. The second mark shows where your bullet will land (13 inches low) at 300 and the third tic (30 inches low) at 400. At 500 yards, the bullet hits near the top of the post.
Faster bullets--say 130-grain .270s--are best zeroed at 200 yards and will hit near the crosshair to 250. At 300 yards the bullet will land about six inches low, near the first hash mark.
I've used the Burris reticle for long-range target shooting and hunting. The best pronghorn buck I've ever shot fell to a .280 Remington bullet at 393 yards--a shot made possible by the Burris reticle and my recent practice with it at ranges to 400 yards.
The mil dot reticle is perhaps the best-known of long-range reticles. "Mil" is an abbreviation for milliradian, 1/6400 of a degree in angular measurement. That's 3.6 inches at 100 yards and three feet at l,000 yards.
In a reticle, a mil is the space between 3/4-minute dots strung vertically and horizontally along a crosswire. To use this reticle as a rangefinder, you divide target height in mils at 100 yards by the number of spaces subtending it. For example, a deer three feet tall at the shoulder (10 mils at 100 yards) appears in your scope to stand two dots high. Divide two into 10, and you come up with five--so the buck is at 500 yards. You can also divide target size in yards (in this case, one) by the number of mils subtended (two) and multiply by 1,000 to get range in yards.
A mil dot reticle must be calibrated for a single magnification. In variable scopes, it's usually the top-end magnification or 10X, but some sights with very high magnification are calibrated at other settings.
After a bit of practice, a mil dot is easy to use. In it you have both a rangefinder and a way to compensate for holdover and drift.
The new Zeiss Rapid-Z reticle is a plex reticle with a ladder of horizontal bars on its lower leg. The short bars extend out to some point in space that marks bullet drift in 21„2 mph wind. Aim with the end of the long bars, and you've compensated for 10 mph wind. Hash marks on the long bars correspond to bullet deflection in a 5 mph wind. Naturally, you must know how fast and from which direction the wind is to make these bars pay off.
More useful to me is the reticle's vertical spacing, calculated to indicate bullet impact in 100-yard increments. The Rapid-Z 600 has four bars below center. The Rapid-Z 800 and 1000 have more bars.
I recently fitted a Victory Diarange 3-12x56 with Rapid-Z 600 to a Savage Model 16 in 7mm WSM. I zeroed at 200 yards, then held an inch low for my first shot at the 100-yard target. The bullet struck right next to my final zero shot.
Because the 7mm WSM could not be assumed to match the trajectory data loaded in the Diarange (you can tailor this scope to your ammo), I allowed myself one preliminary shot at each distance from 300 yards out. My record bullet at 300 struck a couple of inches low and wide enough to four o'clock to indicate a wind gust.
At 400 yards the record bullet landed low in the 10-ring. At 500 yards, using the Diarange bars, I held the length of my arm into the wind. My record round landed 1/2 inch from the target's center--closer than had the 100- and 200-yard shots. In sum, my five-shot group, fired at 100-yard increments from 100 to 500, measured less than four inches. The Rapid-Z works.
Today's long-range reticles have left a generation thinking that distant hits are impossible with standard crosswires. Not so. If the reticle is fine enough to give you a clear view of your target, it will allow you to hit that target. However, the prerequisites of estimating range and holdover are acquired skills, and it's easier if your reticle helps. €¢