How to Sight in a 308 Rifle

Table of Contents

1. Introduction
2. The Foundation of a Precise Zero
3. Essential Gear for Sighting In
4. Pre-Range Preparation: Bore Sighting
5. The Initial Sight-In: The 25-Yard Method
6. Moving to 100 Yards: Refining the Zero
7. Understanding Ballistics and Adjustment Units
8. Environmental and Cold Bore Considerations
9. Ammunition Choice: The Consistency Factor
10. Finalizing the Zero: Slipping the Scales
11. Advanced Considerations for the .308
12. Summary of the Zeroing Process
13. FAQ

Introduction

The .308 Winchester is the workhorse of the tactical and hunting worlds. Whether you are behind a precision bolt gun or a gas-operated battle rifle, the ability to place a round exactly where you want it is the difference between mission success and a wasted pull of the trigger. Sighting in—or zeroing—your rifle is the most fundamental skill an operator must master. At Crate Club, we know that even the best gear in the world is useless if your point of aim does not match your point of impact, so choose your Crate Club tier if you're still building your kit. This process requires more than just poking holes in paper; it demands a disciplined approach to ballistics, mechanics, and marksmanship. In this guide, we will break down the professional method for zeroing your .308 rifle to ensure maximum reliability and precision when it counts.

Quick Answer: Sighting in a .308 rifle involves aligning the optic's reticle with the bullet's point of impact at a specific distance, typically 100 yards. This is achieved by first bore-sighting the rifle, firing a grouping at a close distance (25 yards) to get "on paper," and then refining the adjustments at 100 yards using the optic's windage and elevation turrets. If you are just getting started, start with the Lieutenant tier for a simpler kit.

The Foundation of a Precise Zero

Before you even chamber a round, you need to understand what "zeroing" actually accomplishes. You are aligning the line of sight (what you see through the optic) with the line of bore (the path the bullet travels). Because gravity immediately begins to pull the bullet toward the earth the moment it leaves the muzzle, the bullet travels in an arc.

Your zero represents the specific point where that arc intersects with your line of sight. For most .308 applications, a 100-yard zero is the standard. It provides a flat enough trajectory to engage targets out to 300 yards with minimal holdovers while maintaining extreme precision at closer ranges. If you are using your rifle for professional or defensive use, a 100-yard zero is the baseline from which all your DOPE (Data on Previous Engagements) will be built.

Essential Gear for Sighting In

You cannot zero a rifle effectively if your platform is unstable. Precision requires the removal of as many human variables as possible.

• A Solid Rest: Use a high-quality bench rest or heavy sandbags, and browse the Gear Shop for range essentials that support a stable setup.
• Quality Targets: Use targets with a clear grid system. Most tactical targets use 1-inch or 1-centimeter grids, which makes calculating adjustments much faster.
• Torque Wrench: Before hitting the range, ensure your optic mounts and rings are torqued to manufacturer specifications. Loose rings are the leading cause of "zero shift."
• Eye and Ear Protection: You cannot focus on the fundamentals of a trigger squeeze if you are flinching from the report of the rifle.
• Ballistic Calculator: While not strictly necessary for the zero itself, having an app or card that lists the drops for your specific .308 load will help you understand your rifle's performance beyond the zero point.

We often include high-grade tools and EDC essentials in our Major tier crates that help with field maintenance and gear setup. Having a reliable set of bits and a driver in your range bag is non-negotiable for the serious tactician.

Pre-Range Preparation: Bore Sighting

Bore sighting is the process of aligning the center of the barrel with the center of the optic before you fire a single shot. This ensures that your first round actually hits the target paper, saving you time and expensive .308 ammunition.

Step 1: Secure the rifle. Place the rifle in a steady rest or lead sled. If you are using a bolt-action rifle, remove the bolt. If you are using an AR-10 or similar semi-auto, you may need a laser bore sighter that fits into the chamber.

Step 2: Align the bore. Look through the back of the receiver, down the actual barrel. Center a small, distinct object (like a target bullseye) at 25 or 50 yards through the bore.

Step 3: Align the reticle. Without moving the rifle, look through your optic. Use the windage (side) and elevation (top) turrets to move the reticle until it is centered on the same object you see through the barrel.

Step 4: Double-check. Look through the bore again, then the optic. If they both point at the same spot, you are ready for live fire.

Field Note: Laser bore sighters are great, but How Accurate Are Bore Sights? reminds you that they are not perfect. They get you on paper, but they do not account for the barrel's harmonics or the specific flight path of your bullet. Never trust a laser "zero" without verifying it with live rounds.

The Initial Sight-In: The 25-Yard Method

Many shooters make the mistake of trying to zero at 100 yards immediately. If you are off by even a few inches at 100 yards, you might miss the entire target backing. Start at 25 yards. If you want a fuller walkthrough, How to Sight in a Tactical Rifle Scope covers the same process in a broader format.

Step 1: Fire a three-round group. Aim at the center of the bullseye. Do not worry about where the bullets hit yet; just focus on a consistent point of aim and a clean trigger squeeze.

Step 2: Analyze the group. If your three shots are in a tight cluster, you have consistency. If they are scattered, check your optic mounts and your shooting form.

Step 3: Adjust the turrets. Measure the distance from the center of your group to the center of the bullseye. At 25 yards, the math changes. Most optics are 1/4 MOA (Minute of Angle) per click. One MOA is approximately 1 inch at 100 yards. At 25 yards, one MOA is only 1/4 of an inch. This means it takes four times as many clicks to move the bullet's impact the same distance on the paper.

Step 4: Confirm. Fire another three rounds. The group should now be centered or slightly low (usually about 0.5 to 1 inch low, depending on your optic height) at 25 yards to be close to a 100-yard zero.

Bottom line: Starting at 25 yards ensures you are "on paper" and allows you to identify mechanical issues before moving to the long line.

Moving to 100 Yards: Refining the Zero

Once you are hitting consistently at 25 yards, move your target to 100 yards. This is where the real work begins. At this distance, environmental factors like wind begin to play a role, and any flaws in your shooting position will be magnified. If you need a refresher on dialing corrections, How to Adjust a Sniper Scope is a good companion guide.

Step 1: Fire a five-round group. Three rounds are okay for a rough zero, but five rounds give you a much better statistical average of your rifle's true point of impact. Take your time between shots to let the barrel cool slightly.

Step 2: Calculate the adjustment. Measure the vertical and horizontal distance from the center of the bullseye to the center of your five-round group. If you are using an MOA scope, 1 click = 1/4 inch at 100 yards. If you are using a Mil (Milliradian) scope, 1 click (usually 0.1 Mil) = 0.36 inches at 100 yards.

Step 3: Dial the turrets. If your group is 2 inches low and 1 inch left on an MOA scope, you would dial 8 clicks "Up" and 4 clicks "Right."

Step 4: The confirmation group. Fire a final five-round group. If you have done your part, the cluster should be dead center.

Key Takeaway: A true zero is not a single shot; it is the center of a consistent group. Always adjust based on the average of your shots, not a single "flyer."

Understanding Ballistics and Adjustment Units

To sight in a .308 effectively, you must understand the language of your optic. The two primary systems are MOA and Mils. Neither is inherently "better," but you must know which one you are using. If you want a refresher on the math, How to Use a Rangefinder Scope covers MOA and MIL conversions in context.

Minute of Angle (MOA)

MOA is an angular measurement. 1 MOA is 1.047 inches at 100 yards (widely rounded to 1 inch for simplicity).

• At 100 yards, 1 MOA = 1 inch.
• At 200 yards, 1 MOA = 2 inches.
• At 500 yards, 1 MOA = 5 inches. Most MOA scopes adjust in 1/4 MOA increments, meaning 4 clicks move the impact 1 inch at 100 yards.

Milliradian (Mils/MRAD)

Mils are also an angular measurement, used heavily by the military and professional tactical shooters. 1 Mil is 3.6 inches at 100 yards.

• Most Mil scopes adjust in 0.1 Mil increments.
• 1 click (0.1 Mil) = 0.36 inches at 100 yards.
• 10 clicks (1.0 Mil) = 3.6 inches at 100 yards.

When sighting in your .308, check your turrets. If they say "1/4 MOA" or "0.1 MRAD," do the math based on that specific unit. Mixing these up is a common way to waste ammo.

Environmental and Cold Bore Considerations

In the field, you rarely get a "warm-up" shot, and How to Sight in a Hunting Rifle is a useful reference for that first-round reality. The most important shot a tactician fires is the cold bore shot. This is the very first round fired from a clean, cold barrel.

As you sight in your rifle, you will notice that as the barrel heats up, your group might start to shift or "walk" in a certain direction. This is due to the metal expanding. For a competition shooter, the warm-up group matters. For a hunter or a tactical operator, the cold bore zero is the one you must record.

After you have achieved your perfect 100-yard zero, let the rifle sit until the barrel is cool to the touch. Fire one single round at a fresh target. Note where it hits in relation to your bullseye. This is your "Cold Bore Offset." If it is consistently a half-inch high, you need to know that so you can account for it in a high-stakes situation.

Field Note: Keep a small logbook in your range bag. Record the temperature, altitude, and the specific ammunition you used for your zero. .308 ballistics change significantly between a 90-degree day in the desert and a 20-degree morning in the mountains.

Ammunition Choice: The Consistency Factor

You cannot zero a rifle with 147-grain FMJ (Full Metal Jacket) surplus ammo and expect it to hit the same spot with 168-grain Match Grade or 175-grain Sierra MatchKing rounds. Different bullet weights and powder charges create different barrel harmonics and velocities.

If you are setting up your rifle for serious duty or long-range precision, choose one specific load and stick with it. The .308 Winchester performs exceptionally well with 168-grain and 175-grain bullets in most 1:10 or 1:12 twist barrels.

At Crate Club, our General tier members often receive premium tactical equipment designed to support these high-level platforms. When you are running a high-tier setup, "cheap" ammo is a bottleneck. Always zero with the exact same ammunition you plan to carry in the field.

Finalizing the Zero: Slipping the Scales

Once your rifle is zeroed, your turrets will likely be turned to some random number. To make your optic truly functional, you need to "slip the scales" or "reset to zero."

Most professional optics allow you to loosen a small set screw on the turret cap. This lets you spin the cap so the "0" mark aligns with the indicator line on the scope body without actually changing the internal adjustments. Once reset, tighten the screws. Now, if you have to dial for wind or elevation at long distances, you can always quickly return to your confirmed 100-yard baseline, and shop tactical tools when you want your range kit squared away.

Post-Zero Checklist

• Confirm all mounting screws are still tight.
• Verify the cold bore shot.
• Reset your turrets to the zero mark.
• Record your zero data in a logbook.
• Clean the rifle (but remember, a deep clean may slightly shift your zero for the next few shots).

Bottom line: A zero is a living thing. You must verify it periodically, especially after traveling or if the rifle has been subjected to hard use.

Advanced Considerations for the .308

The .308 is a versatile round, but it has a "rainbow" trajectory compared to faster cartridges like the 6.5 Creedmoor. This means your zero is even more critical. Because the bullet drops more aggressively after 300 yards, a 1-inch error at 100 yards could result in a complete miss at 600 yards.

If you are using a semi-auto platform like an AR-10, How to Use a Tactical Scope is a solid companion for precision setup. Semi-autos require more consistent shoulder pressure than bolt-action rifles to maintain the same zero.

Maintaining Your Kit

Sighting in is only part of the equation. Maintaining the gear that maintains your zero is just as vital. We provide the tactical tools and high-performance gear in our Major XXIII Supply Drop that help you keep your rifle in peak condition. Whether it’s optic cleaning kits, torque drivers, or specialized range gear, staying prepared means having the right equipment ready to go.

Summary of the Zeroing Process

Sighting in your .308 doesn't have to be a chore if you follow a structured process. By removing variables and following the math, you can achieve a professional-grade zero in under 20 rounds.

• Stabilize: Use a bench rest and rear bag.
• Prepare: Bore sight to get on paper.
• Start Close: Use the 25-yard target to find your initial grouping.
• Refine: Move to 100 yards for the final zero.
• Calculate: Use the correct MOA or Mil math for your optic.
• Verify: Confirm with a final five-round group and a cold bore shot.
• Document: Record your settings and ammo type.

Success in the field is built on the foundation of a perfect zero. Take the time to do it right, and your .308 will be a tool you can trust in any environment. For a look at gear that complements field readiness, see the General IX Supply Drop.

Our community of tactical enthusiasts and veterans understands that preparation is a mindset. By joining the Crate Club, you ensure that your gear matches your skill level, with every item field-tested by people who have used this equipment in the most demanding conditions. Explore our subscription tiers to start building a kit that is as ready as you are.

FAQ

Should I zero my .308 at 100 or 200 yards?

For most shooters, a 100-yard zero is superior for a .308. It is the easiest distance to shoot accurately without environmental factors like wind significantly affecting the bullet, and it provides a reliable baseline for using a ballistic calculator or "dialing" for longer distances. A 200-yard zero can work for hunters, but it makes close-range shots more complicated as the bullet will impact significantly high at 100 yards. If you want to compare sighting distances, What Distance to Sight in Your Hunting Rifle gives a helpful framework.

Why does my zero change when I switch ammunition?

Different ammunition uses different bullet weights, shapes (BC), and powder charges, all of which change the velocity and how the barrel vibrates (harmonics). Even a slight change in velocity will cause the bullet to exit the muzzle at a different point in the barrel's vibration cycle, leading to a different point of impact. Always re-zero your rifle if you switch brands or bullet weights.

How many shots should be in a group when sighting in?

While a three-shot group is the minimum to see where you are hitting, a five-shot group is the professional standard for sighting in. Five shots provide a much better representation of the rifle's true accuracy and help you identify if a single outlier was a "flyer" caused by shooter error or if the rifle itself is inconsistent. If you want a closer look at the setup process, How to Boresight an AR Rifle is a useful companion.

What is the difference between MOA and Mils on my scope?

MOA (Minute of Angle) is based on degrees and is roughly equal to 1 inch at 100 yards, while Mils (Milliradian) is a metric-based angular measurement where 1 Mil equals 3.6 inches at 100 yards. Neither is more accurate than the other; the "best" one is simply the one you and your shooting partners understand best. Most modern tactical shooters prefer Mils because the math is easier to calculate in base-10 when shooting at varying distances.