We take a quick look at the 6mm GT cartridge, the “Glorious Tiger” of 6mm chamberings.
The 6mm GT is a 2019 collaboration between George Gardner (GA Precision) and Tom Jacobs (Vapor Trail Bullets). Designed with competition shooting in mind, they wished to create a 6mm cartridge that could use forgiving propellants and feed reliably from AICS magazines. They also wanted the round to extend barrel life yet still provide high muzzle velocities with tight rifling twists to stabilize long, high-BC 6mm bullets.
Accordingly, the 6mm GT has a 35-degree shoulder angle for easy feeding, an optimized case nearing 100 percent capacity with about 35 grains of Varget and develops 3,020 to 3,080 fps with 103- to 105-grain bullets.
The 6mm GT works very well on deer, pronghorn and sheep as a hunting round. The 6mm GT can also be chambered in AR-type semi-autos, though it’s used primarily in bolt guns.
General Comments
Known jokingly as the “Glorious Tiger,” the 6mm GT took off in the PRS and NRL match scene from 2019 onward. From the base to the shoulder junction, the 6 GT case is 0.100-inch longer than the 6mm Dasher, and it has a 35-degree shoulder versus the Dasher’s 40-degree design. Gardner and Jacobs also increased the neck length by 0.050 inch compared to the Dasher, making the brass 0.150-inch longer overall. Both dimensional changes help the 6 GT feed well from unmodified .308-size magazines, unlike the 6mm Dasher. Because it uses less propellant, the 6mm GT marginally increases barrel life compared to the 6mm Creedmoor.
Hornady 6GT brass is available from GA Precision. According to Gardner, the 6mm GT cartridge was specifically developed to use Varget powder, but Hodgdon H4350 is also a good choice. The 6mm GT shoots 107-grain Sierra Match Kings at around 3,015 fps MV with 37.8 grains of H4350. Berger 105-grain Hybrid bullets generate 3,015 fps muzzle velocity with 34.2 grains of Varget. Brass is available from Hornady and Alpha Munitions. GA Precision and Clays Cartridge Co.
supply loaded ammunition.
6mm GT Loading Data and Factory Ballistics
| Bullet (grains/type) | Powder | Grains | Velocity | Energy | Source |
| 105 Berger Hybrid | FL | – | 3,020 | 2,126 | Clays Cartridge Co. 1538 |
| 105 Lapua | N140 | 34.8 | 3,000 | 2,098 | MDTTac.com |
| 108 Berger | N140 | 34.5 | 2,122 | 2,122 | MDTTac.com |
| 109 ELDM | FL | – | 2,035 | 2,035 | GA Precision |
Editor's Note: This article is an excerpt of Gun Digest's Cartridge's Of The World.
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