TESTED: NEW 6GT Brass from Lapua

Lapua brass has been synonymous with winning for years. I’ve had great success with it as have many world-renowned shooters. When Gavin presented me the opportunity to try one of Lapua’s newest brass offerings, 6mm GT, I couldn’t resist trying it for myself.

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About Lapua’s 6mm GT Case

The 6GT has grown in popularity in the competition world but is also a viable hunting cartridge, positioned between the 6.5 Creedmoor and 6mm Dasher.

The 6GT performs with a wide range of bullets, also offering extra case capacity and good speeds.

From Lapua:

New for the autumn of 2024, Lapua will offer a superior choice for competitive shooters with Lapua 6mm GT cartridge cases. Experience unparalleled consistency, quality, and durability with Lapua’s 6mm GT as you pursue excellence in the world of practical precision rifle sports.

The incredible growth witnessed in PRS, NRL, and similar competitive shooting disciplines the past 10 years has heralded the development of high performance, short-action cartridges like the 6mm GT. The GT provides flawless feeding from bolt-action, magazine feed platforms when utilizing the latest high ballistic coefficient 6mm projectiles. Its ultra-efficient cartridge provides low recoil impulse for easy target acquisition and offers excellent precision and velocity consistency.

The Lapua 6mm GT difference: We provide superior cartridge geometry that is based on the original 6.5×47 Lapua parent case. This maximizes longevity and optimizes case capacity for the competitive shooter.

Lab Results

I took a variety of lab measurements on 20 cases to evaluate their consistency.

The average length was 1.7196” with a very, very low standard deviation of 0.0008” and tight extreme spread.

The 6GT cases had an average weight of 157.87 grains with a 0.1586 grain SD and 0.5600 grain extreme spread. Out of all the measurements I took, the one I cared most about was case neck thickness.

The average was 0.01283” with an impressive SD and ES of 0.00025” and 0.00085” respectively. This is on the thinner side, not leaving much to be turned down, but most modern chambers are no-turn chambers. There is still enough meat if you want to turn down the necks, but as shipped this brass has an ideal neck thickness for bullet seating and release.

I also conducted a water capacity test comparing Lapua 6GT cases to Alpha Munitions 6GT cases. The Lapua case held 39.7 grains while the Alpha brass held 40.12 grains — both are in the same range.

Loading and Shooting

I primed a number of cases using a Primal Rights Competition Primer Seater, charged them with 33.5 grains of Varget using an RCBS ChargeMaster Link, and seated Hornady 6mm 105 grain AeroMatch bullets on an Area 419 ZERO press.

Lapua’s brass packaging conveniently doubles as a reloading block.

I fired the loads through two different 6GT rifles, a SIG SAUER Cross with upgrades from ODIN Works and a Bergara in a Foundation Stock.

I achieved the best groups with the SIG cross, three shots going into a 0.53” group at 100 yards and four going into 0.55”.

This is a textbook example of when data on paper doesn’t match data on target. Rounds fired through the Bergara 6GT had an average standard deviation of 4.6 fps compared to 10.35 fps for the SIG Cross with the ODIN barrel.

They also had a higher velocity and smaller extreme spread, not unexpected with a longer barrel.

Conclusion

I was very impressed by the 0.00085” neck thickness spread across the 20 Lapua cases I tested. This incredible consistency is an excellent confidence booster as well.

The 6GT rounds I loaded performed well across two different guns, but I’m certain we could achieve even better results with dedicated load development.