What is 6 mm GT?

Lapua offers top-tier brass in 2024, including for 6 mm GT, while Hodgdon has the load data in its new Basic Reloading Manual.

posted on January 29, 2024
6Mmgt 1
The 6 mm GT wildcat competition cartridge is becoming “legitimized” for handloading with more brass and load data from manufacturers.
Manufacturer photo

New brass from Lapua will help “legitimize” an up-and-coming competition wildcat cartridge, the 6 mm GT. Lapua also announced it will number .300 WSM among its offerings of highest quality brass cases for handloading. Both will be available in 2024.

Lapua's .300 WSM and 6 mm GT brass
Lapua 6 mm GT and .300 WSM brass will be available later this year. (Manufacturer photo)


Lapua’s .300 WSM cases will be available sooner, perhaps as early as spring 2024.

“.300 WSM reloading enthusiasts who insist on using the best components now have Lapua cartridge cases available for their long-range target rifles and custom hunting guns,” Lapua Sales and Marketing Manager, Erkki Seikkula said in a press release.

The 6 mm GT Cartridge

If you haven’t heard of the 6 mm GT cartridge, you aren’t alone. Conceived by George Gardner (of GA Precision) and Tom Jacobs (of Vapor Trail Bullets) and introduced to Precision Rifle Series (PRS) and National Rifle League (NRL) competition in 2019, the competition cartridge is a bridge between the 6 mm Dasher and 6 mm XC. Its purpose is to feed reliably from a magazine, especially AR-15-style magazines, and to extend barrel life and ease load development when replacing a worn barrel.

To the latter ends, the 6 mm GT cartridge was developed specifically to utilize Hodgdon’s Varget powder. Like others in its 6 mm class, the 6 mm GT is also intended to attain high velocity (3,000 f.p.s. and beyond with Berger 105-grain hybrid bullets) from tight-twist barrels. These attributes are why the cartridge is becoming more frequently used in PRS- and NRL-style competition, and is apparently getting the attention of long-range competition shooters, too. All that attention, unfortunately, means supply is having trouble keeping up with demand.

The wildcat might be even more prevalent if brass were more readily available. Though 6 mm GT precision reloading tools are available from Hornady, GA Precision appears to be the sole source for brass (and Hornady, RCBS and Redding dies) at the time of this writing. Though handloaders can form 6 mm GT brass from not-terribly-uncommon 6x47 Lapua brass, factory 6 mm GT brass from Lapua will be a welcome addition to the genre, and Lapua’s timing is right.

“Competitors shooting PRS and similar long-range disciplines have urged us to develop a 6 mm GT case with unmatched quality and superior cartridge geometry to those currently offered in the marketplace,” Lapua’s Vice President of Sales and Marketing, Jarkko Aro said in a press release. “We’re confident we’ve exceeded their demands by collaborating with original cartridge developers, George Gardner and Tom Jacobs.”

Lapua 6 mm GT cases will become available later this year; Lapua’s forecast is for fall 2024, though the company encourages handloaders to order them now through local Lapua dealers.

Free Reloading Manual From Hodgdon

Though Varget is the intended powder of choice for the 6 mm GT, Hodgdon’s new 2024 Basic Reloading Manual lists 67 loads utilizing a dozen or more other powders, in addition to Varget. Here, you’ll find Hodgdon lists the “6 GT” between the 6 mm ARC and 6 mm Creedmoor, and this new manual includes data for plenty of other cartridges to recently hit the range and field as well, such as 7 mm PRC, .22 GT, .360 Buckhammer and 400 Legend.

Hodgdon’s 2024 Basic Reloading Manual
Hodgdon’s free manual includes load data for the newest cartridges. (Photo by Art Merrill)


Despite its name, Hodgdon’s 46-page 2024 Basic Reloading Manual doesn’t teach basic reloading, but it has plenty of basics on, unsurprisingly, powders. Page 14 has interesting information on smokeless powder properties and a “sniff test” for deterioration. Page 16 is mostly a glossary of terms for bullets; page 17 is dedicated to listing 159 smokeless powders in order of their approximate burn rate. Plus, the shotshell section has useful charts on wads and bushings, in addition to load data, along with a half-page on the physics of recoil, including a formula for the math nerds.

Hodgdon’s 2024 Basic Reloading Manual is an excellent addition to the reloader’s reference library, and best of all the price is right—free. You should find it at most retailers who sell smokeless powders and other reloading products. Go to hodgdonreloading.com to learn more.


Uspsamagazine 2024 1
Uspsamagazine 2024 1

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