History
George Gardner of GA Precision designed the 6 GT in 2019 with Tom Jacobs. The 6mm BR and 6mm Dasher already delivered superb accuracy and barrel life, but they are short, fat cases that feed poorly from box magazines, and that was the problem to solve. The 6 GT keeps the mild, accurate character on a slightly longer case sized to feed reliably from AICS-pattern magazines. The result is a purpose-built PRS and NRL cartridge rather than a repurposed benchrest round.
SAAMI standardized it, and factory ammunition and brass arrived from Hornady and Alpha Munitions, which moved it from wildcat to mainstream fast. It fires the same 105 to 110 grain match bullets as its rivals at modest velocities, trading top-end speed for low recoil, long barrel life, and easy load development.
Lineage
The case is purpose-designed, not a necked-down parent: a .473 inch (.308-family) head, a 30 degree shoulder, a small rifle primer, and .243 inch (6.17mm) bullets. It runs in a short action on standard AICS magazines. Its peers are the other efficient 6mm target rounds, the 6mm Dasher, 6mm BRA, 6XC, and the higher-capacity 6mm Creedmoor.
Specifications
| Spec | Value |
|---|---|
| Case type | Rimless, bottlenecked (~30° shoulder) |
| Bullet diameter | 6.17 mm (.243 in) |
| Neck diameter | 6.93 mm (.273 in) |
| Shoulder diameter | 11.66 mm (.459 in) |
| Datum diameter | 9.53 mm (.375 in) |
| Rim diameter | 11.96 mm (.471 in) |
| Case length | 43.82 mm (1.725 in) |
| Overall length | 67.06 mm (2.640 in) |
| Case capacity | ~38 gr H2O (nominal) |
| Primer size | Small rifle |
| Belted | No |
| Rifling twist | 1 in 7 in (recommended, for heavy 6mm match) |
| Max pressure | SAAMI standardized (~62,000 psi) |
| Recommended barrel | 26 in, 1:7 twist |
Barrel Design
Twist is the first decision, and the heavy 105 to 110 grain match bullets settle it. The baseline I'd recommend is 1:7, fast enough to stabilize the longest of those bullets with margin. A 1:7.5 or 1:8 covers the common 105 to 109 grain loads, but the faster twist has no downside and protects the heaviest options.
This is a mild, efficient case, not an overbore one. It reaches useful velocity in a sensible barrel and gives you long accuracy life, so the baseline I'd recommend sits at 26 inches, enough to collect the velocity the case has to give without chasing diminishing returns. Where the overbore 6mm magnums burn their throats quickly, the 6 GT does not, and barrel life is one of its main selling points.
The tables below are computed at that 26 inch barrel. The range load is scaled from Hornady's 24 inch factory figure, so confirm your own on a chronograph before trusting any dial.
Match Ammo Performance
Hornady Match · 109 gr ELD Match $1.90/rd
| Range (yd) | Velocity (fps) | Elevation (mil) | Energy (ft-lb) | Windage (mil) |
|---|---|---|---|---|
| 0 | 2920 | -0.4 | 2063 | 0.3 |
| 100 | 2769 | 0.0 | 1856 | 0.2 |
| 200 | 2622 | -0.4 | 1664 | 0.3 |
| 300 | 2480 | -1.0 | 1488 | 0.5 |
| 400 | 2342 | -1.7 | 1327 | 0.7 |
| 500 | 2209 | -2.5 | 1181 | 0.9 |
| 600 | 2080 | -3.3 | 1047 | 1.1 |
| 700 | 1955 | -4.3 | 925 | 1.3 |
| 800 | 1835 | -5.3 | 815 | 1.5 |
| 900 | 1717 | -6.4 | 714 | 1.8 |
| 1000 | 1603 | -7.7 | 622 | 2.0 |
| 1100 | 1493 | -9.0 | 539 | 2.3 |
| 1200 | 1385 | -10.5 | 465 | 2.6 |
| 1300 | 1283 | -12.2 | 398 | 3.0 |
| 1400 | 1185 | -14.0 | 340 | 3.3 |
| 1500 | 1103 | -16.1 | 295 | 3.7 |
Muzzle velocity 2920 fps is estimated at 26 in from the 24 in factory figure of 2870 fps at about 25 fps per inch. Expect your own barrel to read a little differently. Velocity is color coded green supersonic, yellow transonic, red subsonic; treat transonic and subsonic rows as approximate.
Trajectory
FAQ
What barrel length and twist should I run?
A 1:7 twist for the heavy 105 to 110 grain 6mm match bullets, and a 26 inch barrel to collect the velocity. The 6 GT is efficient rather than overbore, so there is little to gain from a longer barrel and a great deal of barrel life to enjoy from a sensible one.
Is the 6 GT a SAAMI cartridge?
Yes. The 6 GT is SAAMI standardized, with factory ammunition and brass from Hornady and Alpha Munitions. The dimensions on this page come from the SAAMI drawing. That standardization, and reliable magazine feeding, are what separate it from the 6mm BR and Dasher it competes with.
How does it compare to the 6mm Dasher and 6mm Creedmoor?
The 6 GT matches the Dasher's efficiency and accuracy while feeding far better from magazines, which is why it took hold in PRS. Against the 6mm Creedmoor, it gives up some velocity and case capacity for less recoil and longer barrel life, a trade many competitors accept.
What is it good for?
Practical precision-rifle competition (PRS and NRL) and any target shooting inside about 1,000 yards where low recoil, easy spotting, and long barrel life matter more than raw velocity. It is not a long-range hunting or ELR cartridge; the heavier 6.5s and .30s do that job.