September 23, 2010
By David Tubb
They don't count for score, but the two shots you fire first really matter.
By David Tubb
Doing sighters right starts with watching conditions. After your first one, you need to make a full correction if you're going to learn what's happening to your bullets downrange.
We get two sighting shots prior to each event in an NRA High Power Rifle tournament. These sighting shots are the only ones we're allowed that don't count toward score, but they largely determine our success. The outcome of those two sighters provides feedback the shooter uses to determine a sight setting that he will use to start the string.
Last issue we covered the "no-wind zero," a sight setting that will, under calm conditions, produce a centered group at one yard line. I use the 300-yard prone rapid-fire event to determine my no-wind zero. Each "event zero" is the routine change from this setting that will, under the same conditions, produce a centered group for each specific event: 200-yard standing, 200-yard sitting and 600-yard prone.
Let's now think about going from the 300-yard line back to 600. First, I take the rear sight to my 600-yard event zero, then I try to figure out what's going on with conditions. I rely on many inputs to determine initial correction for the first sighter. I've been watching the wind, watching other shooters' targets come up--always experiencing and gauging the environment. There's a lot to look for, and some things are of more significance under different prevailing conditions.
When I get to the line and prepare for my first sighter, I have a setting in mind, and I put that on the sight for my test shot. I fire it and immediately get back to watching conditions. When the target comes up and I see the location of the shot, I get the first piece of the puzzle. I make a full correction off the impact location of that first sighter. Always make a full correction. That means move the sight the number of clicks that would have resulted in a center X.
I may have noted a change in conditions from the time I fired that first round and when the target came up, but I will still follow that advice even if the condition change might have been worth a click or two. I'm not playing a sighting-in game. I am determining the value of prevailing conditions. Then, on the second sighter, I confirm my decision. If it was too much or not enough, then I'll know, and now I'll have the odds in my favor that my third round--the first record shot for score--will be centered.
The only exception to this advice is when conditions are changing rapidly or shifting toward extremes. From watching beforehand, I will already have seen this and will attempt to fire one sighter at what I have determined is the high end of the change and the other at the low end. This is a good process to follow when the wind is fishtailing.
Too many shooters second-guess themselves--and the conditions--too much. Sighters are for learning about condition effects. It is far better to over-correct than to under-correct after the first sighter. If you fire it on the same setting as the first, then you didn't learn as much.
This is the procedure I follow when I'm on the firing line, but there are things I do beforehand that are equally helpful. For one thing, you need to know whether that first shot from your rifle is providing accurate feedback.
Most shooters know to expect the first shot from a clean barrel to be outside the usual group. Sometimes it's more than one shot. The amount of this change, and the number of rounds necessary to overcome it, can vary widely depending on ammunition, cleaning methods and so on. I am not normally going to the 600-yard line with a clean barrel, but that's often the case when I attend a Long Range Rifle event.
Anything that can be done to enhance early-shot consistency is extremely valuable. To that end, I have determined three influences that start back in the shop and one that's now done on the firing line.
I'm convinced that it is unwise to mix loads--using bullets from a different maker at more than one event on the same day or using a different propellant brand or type in the same way. I learned this through a good deal of testing at 1,000 yards.
I always use the same brand bullet and very same propellant for all my loads. It's okay to change bullet weights, just as long as they're built on the same jacket material. Never mix coated and uncoated bullets. Your zero will return but not right away, and it's "right away" that matters when faced with a sighting shot.
I have long been a proponent of coated bullets but have recently changed my material preference from moly to boron-nitride. BN coating goes on clear and seems to have none of the drawbacks some claim for moly. Performance increases are virtually identical.
The unexpected side benefit I have found from BN coating is that my first shot from a clean barrel goes onto the same point as my last shot in an event. That, especially on the 1,000-yard line, is worth at least a "half a sighter," maybe more. I'm using nothing but BN-coated bullets now and likewise have geared my own ammunition company toward producing them.
Over the past three years, I have come to rely much more on mathematics to help me determine my first-shot zero. I am not, however, using a conventional ballistics program. A colleague and I developed a more accurate and comprehensive system that can encapsulate condition influences without doing any "math" on the spot. All calculations have been done previously.
Essentially, I have been factoring density-altitude into my initial corrections and have, especially in Long Range Rifle events, been fantastically happy with the results. My first shots are now much closer to my last ones.
I'm using custom-done charts and carry these with me to every event. Learning to use the density-altitude factor answers questions of how temperature and altitude will influence bullet impact. It allows you to precisely determine, for instance, what will happen when it's 90 degrees one day and 65 the next, as can be the case at Camp Perry.