Rifles 102: Precision & Accuracy

The Precision.

Projectile placement is a hunting debate outside the scope of this piece. We will assume a 10-inch target encompassing the lungs and heart. Placement in this target is a function of accuracy, and accuracy must be preceded by precision if it is to be repeatable. 

We define precision adequate for hunting as multiple successive 10 round groups which fall within the target size. This means that for our 10” target, a 2 MOA gun is required to shoot to 500 yards and a 1 MOA gun is required to shoot to 1,000 yards. Given that most hunting engagements take place under 300 yards, a 1.5-2” 10 shot group at 100 yards is more than sufficient for most hunters, and not the limiting reagent most believe it to be. The more precise the rifle system, the more allowable error for shooter technique and firing solution.

Precision derives not only from rifle setup criteria, but equally from shooter technique & position. The shooter should build a solid position where the forend of the rifle is supported by a soft unattached bag, and the rear of the rifle is supported by a soft unattached bag. Vertical adjustments should be made by squeezing the rear bag, not by introducing muscle torque directly into the rifle itself. The eye should be moved around the eyebox while the parallax knob is turned to ensure the crosshairs are true at a given distance. When the trigger is pressed, no motion or anticipation should be exerted on the rifle. The shooter should stay glued to the rifle, tracking the vapor trail if any and the impact if any. Without staying “on the rifle,” precision is very difficult. Recoil should not be an obstacle. If it is, you should reduce the recoil even at the expense of carrying a heavier/longer rifle or shooting a lesser cartridge to a shorter maximum range. No single factor is more important in hunting success than the proper engagement of the rifle and shooter.

The Ammo.

Once you have selected a cartridge which your rifle system shoots well, you should stock up on it. If you’re a reloader, that means hoarding components of the same lot. If you’re not: I suggest the following process for those buying factory ammo:

1. Buy a single box of as many factory loadings of your chosen projectile(s) as practical. Four is a good minimum number. For example, in 6.5 creedmoor:

1. Hornady 140 ELD-M

2. Hornady 143 ELD-X

3. Hornady 147 ELD-M

4. Barnes VOR-tx 127 LRX

5. Sierra 130 TMK

6. Berger 156 EOL

2. After establishing a workable near-zero from boresight (a couple of rounds of cheap range ammo), fire 10 round groups at 100 meters using each box of ammo candidates.

1. Do not remove your face from the rifle while shooting these groups. Use a friend to reload your magazine. 

2. Do not wait for the rifle to cool within each 10 round group. Good rifles do not spray rounds when hot, better to find out now rather than later. 

1. No, it doesn’t matter that it has a “pencil barrel,” this is a heat treat problem.

3. Once you’ve fired each 10 round group, use the Hornady 4DOF app’s group analysis tool or BallisticX to assess mean radius and total angular (MOA) size.

1. Select the cartridge which produces the best results. 

2. Move the center of its group to zero with your turrets.

3. Fire the last 10 rounds of the box at the zero to confirm you are now zero’d.

4. Slip your turrets.

4. Buy an entire barrel life’s worth of ammo now.

1. Ensure you order the correct lot number. Call the retailer to ensure. Ammo varies in velocity and point of impact from lot to lot.

2. Buying a full barrel life of ammo is expensive now (and probably impractical for very long lived barrels like .308) but you will never have to re-zero again, and that is a major cost savings at 2 bucks a round.

The Accuracy.

Once precision is achieved, accuracy follows from quality of zero, quality of wind call, and quality of range elevation correction.

There is nothing more powerful than the feeling of knowing that a round will go precisely where your crosshairs lie, so long as your math (firing solution) is right. In order for that to be the case, you must achieve a rock-solid 100 yard zero and maintain that zero over time. Take your time when you zero, don’t settle for subpar atmospheric conditions (crosswinds over 3mph), and don’t allow target panic to rush your shots. While your elevation corrections will vary wildly, remember that your zero will not substantially move from the bottom of Death Valley in summer to the summit of Denali in winter. Shifts in zero are a system problem, not an environmental problem, and should not be tolerated.

The NSI philosophy emphasizes setting up a rifle once, properly. While a 30 round zero might sound excessive, it is done once per barrel and pays dividends in ensuring the true cone of fire of the rifle is lined up with the optics for long range accuracy. In rifle systems which lose zero yearly, this might be an unbearable expense. An NSI rifle losing zero is not business as usual - it is an anomaly and a warranty event.

Calling wind is an art beyond the scope of this piece, but you should not be hunting at ranges and in winds where more than a .5 mil (1.7 MOA) wind call is required. Using a high-BC bullet design further limits your wind call risk. Attend classes to improve your wind calling skill: it is the only true “art” in what is otherwise a highly rational and scientific process.

You must know your current enrivonmentals and true distance & slope to target in order to adjust elevation properly. Rely on a quality rangefinder and ballistic solver for this. Binocular rangefinders are more stable than monoculars. Mounting on a tripod increases stability yet further. Using an anemometer like a Kestrel will provide not only wind but Density Altitude - a single figure which encompasses temperature, pressure, and altitude as an input to your ballistic calculator.