Why Should You Boresize Paintballs?

When it comes to paintball accuracy, consistency, and air efficiency, players often focus on markers, barrels, and paint quality—but paintball bore sizing is just as critical. Choosing the correct barrel bore size for your paintballs can significantly improve shot consistency, reduce breaks, and help you get the most performance from your marker. Matching your paintballs to the correct barrel bore size can dramatically improve accuracy, consistency, and air efficiency. Whether you're a beginner or a seasoned player, understanding bore sizing can help you get the most out of your setup.

What Is Paintball Bore Size?

Paintball bore size refers to the internal diameter of a paintball barrel and plays a major role in how efficiently and accurately your marker shoots.

Bore size refers to the internal diameter of a paintball barrel, typically measured in inches (e.g., .679, .684, .689). Paintballs themselves vary slightly in size due to factors like brand, manufacturing batch, temperature, and humidity. Because paintballs aren’t perfectly uniform, matching them to the right barrel bore is essential for optimal performance.

Why Paintball Bore Sizing Matters

1. Improved Paintball Accuracy

When a paintball fits properly in the barrel, it travels straight and true. A ball that is too small for the bore can bounce inside the barrel, while one that’s too large can cause drag or even break. Proper bore sizing helps ensure consistent shot-to-shot accuracy.

2. Increased Air Efficiency & Consistent Velocity

A correctly sized paintball creates an effective air seal in the barrel. This allows your marker to use air more efficiently, resulting in more shots per tank and more consistent velocity. Poor bore matching can waste air and reduce overall performance.

3. Fewer Paintball Breaks

Overly tight bores increase friction and pressure, which can lead to barrel breaks—especially with brittle tournament paint. Matching paint to bore size reduces stress on the ball and helps keep your barrel clean during games.

How to Match Paintballs to Barrel Bore Size

The Drop Test (Best Way to Size Paintballs)

The most popular and simple method is the drop test:

• Remove your barrel from the marker
• Drop a paintball into the barrel
• The ideal fit allows the ball to sit in place or slowly roll out with a gentle breath of air

If the ball falls straight through, the bore is too large. If it doesn’t move at all, the bore is too small.

Overboring vs. Underboring Explained

• Overboring (barrel slightly larger than the paint) is popular for consistency and reduced breaks, especially in changing weather conditions.
• Underboring (barrel slightly smaller than the paint) can improve air efficiency but increases the risk of breaks.

Most players prefer a slight overbore for reliability.

How Weather Affects Paintball Size

Paintballs shrink and expand based on environmental conditions:

• Cold temperatures cause paint to shrink
• Heat and humidity can cause paint to swell

This means bore sizing isn’t a “set it and forget it” process. Tournament and serious recreational players often recheck bore size throughout the day as conditions change.

Do You Need a Paintball Barrel Kit?

A barrel kit such as the Freak XL Kit includes multiple bore inserts, allowing you to match your barrel to different paint sizes. While not mandatory for casual play, barrel kits are highly beneficial for competitive players who want maximum performance and flexibility.

Final Thoughts on Paintball Bore Sizing

Bore sizing is one of the most overlooked yet impactful aspects of paintball performance. Taking the time to match your paintballs to the correct barrel bore can improve accuracy, consistency, air efficiency, and overall reliability on the field.

If you’re serious about stepping up your game, understanding and applying proper bore sizing is a simple upgrade that delivers noticeable results.

Paintball Bore Sizing FAQ

What is the best bore size for paintball?
There is no single “best” bore size, as paintballs vary by brand, batch, and weather conditions. Most players commonly use bore sizes between .679 and .689, with a slight overbore being the most reliable setup.

Does bore size affect accuracy?
Yes. Proper paint-to-barrel matching improves shot consistency and reduces flyers caused by excess barrel movement or air loss.

Is a tighter bore more accurate?
Not always. Extremely tight bores may increase air efficiency but often lead to more barrel breaks. Consistency matters more than tightness.

Final Thoughts on Paintball Bore Sizing

Paintball bore sizing is one of the simplest and most effective ways to improve accuracy, consistency, and efficiency. By matching your barrel bore size to your paintballs—rather than forcing paint to fit your barrel—you’ll experience fewer breaks, smoother shots, and more reliable performance on the field.

Whether you’re a casual player or a tournament competitor, understanding how to choose the right paintball bore size gives you a measurable advantage.

Pro Tip: Always match your barrel to your paint—not the other way around. Even the best barrel can’t fix poorly sized paintballs.