As a long-time shooter, reloader, and outdoor enthusiast, I’ve spent countless hours chasing the holy grail of accuracy. Whether I’m preparing for a precision rifle competition, dialing in a hunting load, or simply enjoying a day at the range, consistent, tight groupings are the ultimate reward. And a critical, often overlooked, component of achieving that accuracy is bullet concentricity. That’s where a sinclair concentricity gauge, or a similar bullet concentricity gauge, comes into play. In this guide, we’ll explore everything you need to know about how to measure concentricity, why it matters, and which reloading concentricity gauge is right for you. We’ll also cover the RCBS concentricity gauge and other popular options, including the Accuracy One concentricity gauge.
Simply put, bullet concentricity refers to how well the bullet’s axis aligns with its overall length. Ideally, the bullet should be perfectly centered within the cartridge case. When a bullet isn’t concentric – meaning it’s off-axis – it introduces several problems during the firing process. As the bullet travels down the barrel, this misalignment causes it to wobble or deviate from a straight path. This wobble increases drag, reduces velocity consistency, and ultimately, widens group sizes. Think of it like spinning a football; a perfectly thrown spiral travels further and more accurately than one that’s tumbling. The same principle applies to bullets.
Factors contributing to poor concentricity include:
There are several types of gauges available to check concentricity, each with its own strengths and weaknesses. Choosing the right one depends on your budget, reloading volume, and desired level of precision.
These are the most common and affordable type. They typically consist of a V-shaped cradle that supports the cartridge case, allowing it to spin freely. You observe the bullet’s wobble as it rotates. More wobble indicates greater misalignment. The RCBS concentricity gauge is a prime example of this type, known for its simplicity and ease of use. These gauges are great for quickly identifying problematic rounds, but they offer less precise measurements.
These gauges, like the Accuracy One concentricity gauge, utilize a dial indicator to measure the runout (the amount the bullet deviates from a straight line) in thousandths of an inch. They provide a much more accurate and quantifiable measurement than spinning gauges. They are more expensive and require more setup time, but they are invaluable for serious reloaders striving for maximum precision. These gauges often require a separate stand or mounting system.
Some reloaders incorporate a concentricity check after sizing the case. This helps identify cases that have been distorted during the sizing process and should be set aside. This is a more advanced technique, but it can significantly improve overall accuracy. REI Expert Advice recommends checking case runout at multiple stages of the reloading process.
Let’s walk through the process of using a spinning concentricity gauge (like the RCBS) and then an indicator gauge (like the Accuracy One).
The National Park Service and USDA Forest Service often recommend responsible shooting practices, which include ensuring ammunition is accurate and safe.
| Gauge | Type | Price Range (USD) | Accuracy | Ease of Use |
|---|---|---|---|---|
| RCBS Concentricity Gauge | Spinning | $50 - $80 | Low | High |
| Accuracy One Concentricity Gauge | Indicator | $200 - $300 | High | Medium |
| Sinclair Concentricity Gauge | Spinning | $60 - $90 | Low | High |
| Forster Coaxial Concentricity Gauge | Indicator | $250 - $350 | High | Medium |
Simply identifying poor concentricity isn’t enough. You need to address the underlying causes. Here are some tips:
While a sinclair concentricity gauge is a valuable tool, it’s important to remember that it’s just one piece of the puzzle. Other factors that can affect accuracy include:
Investing in a bullet concentricity gauge, whether it’s a simple spinning gauge or a more sophisticated indicator gauge, is a worthwhile investment for any serious reloader. By understanding how to check concentricity and taking steps to improve it, you can significantly enhance the accuracy of your handloads and enjoy more satisfying results at the range. Remember, chasing accuracy is a continuous process, and attention to detail is paramount. Don't forget to always follow safe reloading practices as outlined by reputable sources like Leave No Trace principles for responsible outdoor recreation.
For more information on reloading techniques, check out our article on Advanced Case Preparation Techniques or our guide to Choosing the Right Reloading Press.