What Caliber to Convert to 6mm BR? A Comprehensive Guide for Precision Rifle Enthusiasts
Converting a rifle to 6mm BR is a popular choice among precision shooting enthusiasts, offering a compelling blend of accuracy, velocity, and manageable recoil. But the "best" caliber to convert from depends heavily on your existing rifle's action, barrel length, and your overall goals. This guide breaks down the factors to consider and suggests suitable candidates for conversion.
Understanding the 6mm BR: Why Convert?
The 6mm BR (6mm Bench Rest) is renowned for its exceptional accuracy potential in bench rest shooting and long-range precision rifle competitions. Its relatively small case capacity results in manageable recoil, allowing for precise shot placement even over extended ranges. The cartridge's inherent accuracy is further amplified by its efficient burning rate and consistent performance. Conversion is often undertaken to upgrade an existing rifle platform to leverage these advantages.
Key Factors Affecting Conversion Feasibility
Before diving into potential source calibers, understand the critical factors impacting conversion:
-
Action Type: The receiver and bolt face of your existing rifle must be compatible with the 6mm BR's case dimensions. Some actions, like those designed for cartridges with smaller bolt faces (e.g., .223 Remington), will require significant modifications or are unsuitable for conversion. Actions designed for larger cartridges (e.g., .308 Winchester) usually offer more flexibility.
-
Barrel Length and Twist Rate: Barrel length significantly influences velocity. While the 6mm BR performs well with various barrel lengths, a longer barrel (24-28 inches) is generally preferred for optimal velocity and accuracy. The twist rate (the number of inches it takes for the rifling to complete one full rotation) is critical for stabilizing the 6mm BR bullet. A 1:8" or 1:7.7" twist rate is commonly recommended. Your existing barrel may need to be re-barreled with a new barrel of appropriate length and twist.
-
Budget: Conversion can involve substantial costs, including barrel replacement, chambering, headspace adjustment, and potentially action work. Plan accordingly.
Suitable Calibers for Conversion to 6mm BR
Several calibers lend themselves better to conversion than others. The best choice will always depend on your specific rifle, but here are some strong contenders:
1. .223 Remington/5.56x45mm: While requiring significant work (possibly a new bolt face), a .223 Remington platform can be converted but necessitates a significant investment. The smaller case size needs to be substantially altered.
2. .243 Winchester: This is a more straightforward conversion than the .223. The case is larger, minimizing modification needs. However, you’ll likely still need a new barrel with the correct twist rate.
3. 6.5 Grendel: Similar in case size to the 6mm BR, this conversion may be more feasible, potentially requiring only a barrel swap and chambering. The bolt face compatibility needs to be verified first.
4. 6mm ARC: The 6mm Advanced Rifle Cartridge is quite close in overall dimensions, and conversion might be relatively straightforward, possibly only requiring a barrel and chamber work.
5. .308 Winchester: This popular caliber provides ample room for modification and is suitable if your action allows. However, extensive work is likely needed, including re-barreling, and potentially action work. This will involve the most significant conversion costs.
Less Suitable Calibers
Calibers with significantly different case dimensions or bolt face sizes will present major challenges, rendering conversion impractical or prohibitively expensive. These include calibers like the .300 Winchester Magnum, .270 Winchester, and others.
Conclusion: Proceed with Informed Decisions
Converting a rifle to 6mm BR is a significant undertaking. Careful consideration of the factors outlined above—action compatibility, barrel requirements, budget, and desired accuracy—is paramount. Consulting with a qualified gunsmith experienced in custom rifle builds is crucial to ensure a successful and safe conversion. Remember, proper headspace is critical for safe operation. Don't attempt this modification without professional assistance.
