The Significance of Safe Headspace
Headspace, in its simplest definition, refers to the distance between the bolt face (the surface that contacts the rear of the cartridge case) and a specific datum point in the chamber (usually the shoulder or the rim of the cartridge). Precise headspace is essential for several critical reasons. Firstly, it allows for proper cartridge alignment within the chamber. Secondly, it ensures the cartridge is supported correctly during firing, preventing catastrophic failures. Without proper headspace, a firearm is at an elevated risk of malfunction and potential injury to the shooter and those nearby.
What Problems Can Occur?
Too little headspace can lead to a failure to chamber the cartridge. On the other hand, excessive headspace can allow the case to stretch excessively upon firing, potentially leading to a case separation. This separation will cause gas and debris to vent backward, posing a severe danger to the shooter. Other issues that can arise from improper headspace include erratic extraction of spent casings, failure to extract, and decreased accuracy. Therefore, correctly measuring and managing headspace is not just a technical exercise; it’s a fundamental aspect of firearm safety and responsible gun ownership.
The Tools of the Trade: “Go” and “No Go” Gauges
To accurately measure headspace, specialized tools known as “Go” and “No Go” gauges are employed. These gauges are precision-made, hardened steel tools designed to replicate specific cartridge dimensions. They are typically cylindrical or stepped in shape, with precisely machined dimensions to correspond to critical measurements.
Understanding Gauge Types
The “Go” gauge is designed to represent the minimum allowable headspace. When properly inserted into the chamber, the bolt *should* completely close and lock. This indicates that the chamber is within the minimum headspace specification. The “No Go” gauge, on the other hand, represents the maximum allowable headspace. The bolt *should not* fully close and lock when this gauge is inserted. If it does, it indicates that the headspace is too long, which could cause serious issues.
The Field Gauge
A third gauge, the “Field” gauge, provides an additional layer of safety. It represents a slightly longer headspace than the “No Go” gauge. The “Field” gauge, if the bolt closes completely on this gauge, indicates the firearm may be reaching the end of its safe service life or is outside of specifications, and immediate inspection by a qualified gunsmith is necessary.
Dissecting the 5.56 NATO Chamber
The 5.56x45mm NATO cartridge is a military cartridge adopted for use in various firearms. The chamber dimensions for this cartridge are standardized to ensure interchangeability and safe operation in rifles across many different manufacturers. These standards are critical to maintain accuracy and ensure safety. Variations in chamber dimensions can lead to problems ranging from poor accuracy to dangerous malfunctions.
Standardization and Safety
The chamber design is meticulously crafted to support the cartridge during firing, ensuring a reliable seal and facilitating proper gas expansion. This design is achieved through precision manufacturing, with each chamber being bored, reamed, and inspected to meet stringent specifications. The goal is to consistently produce a chamber that safely and reliably accommodates a range of different ammunition. The adherence to these standards is what gives the 5.56 NATO cartridge its universal popularity.
The Step-by-Step Guide to Gauging
Before beginning, prioritize safety. **Always ensure your firearm is completely unloaded.** Remove the magazine, and visually inspect the chamber and receiver to confirm the absence of any ammunition. Wear appropriate eye protection. The procedure is as follows:
Preparing for the Gauging Process
1. **Prepare the Firearm:** Thoroughly clean the chamber and bolt face. Remove any oil, debris, or carbon buildup. This will ensure an accurate reading.
Using the “Go” Gauge
2. **Insert the “Go” Gauge:** Insert the “Go” gauge into the chamber. Slowly close and lock the bolt. The bolt should close and lock fully. This confirms that the chamber meets the minimum headspace requirements. If the bolt closes, proceed to the next step.
Using the “No Go” Gauge
3. **Insert the “No Go” Gauge:** Insert the “No Go” gauge into the chamber. Attempt to close and lock the bolt. The bolt *should not* close and lock fully. If the bolt closes, this indicates that the headspace may be excessive and potentially unsafe.
The “Field” Gauge Procedure
4. **Insert the “Field” Gauge (Optional, but Recommended):** Insert the “Field” gauge into the chamber. Attempt to close and lock the bolt. If the bolt closes, it’s essential to have the rifle inspected by a qualified gunsmith immediately. The “Field” gauge is designed to provide an additional level of safety, flagging rifles that may be approaching the end of their safe service life, or have issues that must be addressed.
Important Precautions
It is important to cycle the bolt slowly and deliberately during this process. Avoid forcing the bolt or attempting to overcome any resistance. If a gauge appears to be stuck, carefully and gently remove the bolt and re-evaluate the process to find what went wrong.
Interpreting the Results: What Does it Mean?
The results of the gauging process provide a clear indication of the firearm’s headspace condition.
Ideal Scenario
**”Go” Gauge Closes, “No Go” Gauge Does Not Close:** This is the ideal scenario. The headspace is within the acceptable range. Your firearm is likely safe to operate.
Headspace on the Longer End
**”Go” Gauge Closes, “No Go” Gauge Closes, “Field” Gauge Does Not Close:** This signifies that the headspace is on the longer end of the acceptable range, but still likely safe. Monitor for signs of excessive case stretching, such as bulges in the case upon ejection. If you are seeing case bulging, seek a gunsmith’s opinion.
Headspace Too Long
**”Go” Gauge Closes, “No Go” Gauge Closes, “Field” Gauge Closes:** This is a warning sign. Headspace may be too long. Cease firing the firearm immediately and have it inspected by a qualified gunsmith. Do not use the firearm until it has been inspected and repaired.
Headspace Too Short
**”Go” Gauge Does Not Close:** The headspace is too short, and the firearm could have issues with chambering ammunition. Do not attempt to force the bolt. Consult a gunsmith to diagnose the issue.
Potential Causes and Solutions
Problems with headspace can stem from various causes. Barrel wear over time can slowly increase headspace. Improper barrel installation can also be a factor. Additionally, manufacturing errors can lead to incorrect chamber dimensions. Excessive headspace may result from firing high-powered rounds in a worn chamber.
Addressing the Problem
The solution to a headspace issue depends on the severity. For minor deviations, a qualified gunsmith may be able to remedy the problem. For more severe issues, barrel replacement may be the best or only option. Regular and thorough examination of your firearm’s headspace is the most important preventative step to take to prevent these issues.
Maintaining Your Gauges: A Small Investment in Safety
Go and No Go gauges are durable tools, but proper care is crucial to ensure their accuracy and longevity. After each use, clean them thoroughly with a gun cleaning solvent. Store them in a dry, protected environment to prevent rust and corrosion. Inspect them periodically for any signs of damage or wear. Any damage can compromise the accuracy of the readings. These gauges are an investment in your safety and the safety of those around you.
Conclusion: Safety First, Always
Understanding and utilizing “Go” and “No Go” gauges for 5.56 NATO rifles is an essential component of responsible firearm ownership. By regularly checking headspace, you are actively taking steps to ensure your rifle operates safely and reliably. While this article offers a thorough explanation, the complexities of firearms maintenance and repair necessitate professional expertise for any serious issues. If you encounter any problems during the gauging process or have any doubts about the functionality of your rifle, always consult a qualified gunsmith. Safe gun ownership is a continuous process that requires knowledge, vigilance, and a commitment to safety. Prioritize it, and enjoy the sport and responsibility of responsible gun ownership.
Resources to Help You Further:
- Manufacturer’s websites: Many gauge manufacturers provide detailed instructions and information about their products.
- Gunsmithing Guides: Numerous books and online resources offer in-depth information about firearm maintenance and repair.
- Firearm Safety Courses: Consider taking a local course from a certified instructor for hands-on guidance.
