6mm GT (Handloader issue #358)

The 6mm GT (6mm “GAP Temp”) was introduced in 2020 through a collaboration between George Gardner of GA Precision, renowned competitive shooter Tom Jacobs, and ballistician Clay Blackketter. The cartridge was designed specifically to address the shortcomings of existing precision rifle cartridges by combining the accuracy and efficiency of the 6mm BR family with improved feeding reliability from detachable box magazines. Rather than simply necking an existing case up or down, the designers created a purpose-built cartridge with an optimized shoulder angle, body taper, and overall case dimensions. The result was a cartridge capable of launching modern high-ballistic-coefficient 6mm bullets at competitive velocities while maintaining excellent consistency, long barrel life, and smooth magazine feeding.

The 6mm GT quickly gained widespread acceptance in Precision Rifle Series (PRS) and National Rifle League (NRL) competition because it strikes an excellent balance between speed, recoil, and barrel longevity. Typical loads propel 105- to 115-grain match bullets at approximately 2,900 to 3,000 feet per second, providing flat trajectories, excellent wind resistance, and mild recoil that allows shooters to spot their own impacts. Compared to cartridges such as the 6mm Creedmoor, the 6mm GT generally uses less powder while producing similar practical performance and extending barrel life. At the same time, it offers greater velocity than the classic 6mm BR while maintaining the superb accuracy for which the BR family is known.

Handloaders have embraced the 6mm GT because it was designed with precision loading in mind. High-quality brass from manufacturers such as Alpha Munitions and Hornady has become readily available, and the cartridge performs exceptionally well with temperature-stable powders and modern match bullets. Its efficient case design produces excellent ignition characteristics, low extreme spreads, and consistent accuracy over long shot strings. The cartridge also requires relatively little case preparation compared to many wildcats, making it attractive to competitive shooters who demand both performance and ease of loading.

Although the 6mm GT was created for long-range competition, its inherent accuracy and efficiency have also made it popular among recreational precision shooters and varmint hunters. In only a few years, it has become one of the most successful modern competition cartridges, demonstrating that thoughtful engineering can improve reliability without sacrificing the exceptional precision expected from a purpose-built target round. The 6mm GT continues to establish itself as one of the premier cartridges for precision rifle competition and precision handloading.

Source: Handloader Issue #358 – October 2025