AUSA 2023: Sig Sauer details toxic fume fix for NGSW

Sig Sauer displays its XM250 automatic rifle at the AUSA 2023 annual conference. (Janes/Meredith Roaten)

As the Next Generation Squad Weapon (NGSW) programme enters its limited-user test phase, Sig Sauer says its XM7 and XM250 meet the army's requirements for toxic fumes.

The replacement for the M4/M4A1 carbine weapon, the XM7, and the replacement for the M249 squad automatic weapon, the XM250, both had pressure built up in the chambers of the weapons that led to toxic fumes being pushed out, Jason St John, senior director of government products at manufacturer Sig Sauer, told Janes at the Association of the United States Army (AUSA) 2023 annual conference.

Design upgrades to baffle and to the propellant formula in the new 6.8 mm ammunition fixed the issue, St John said. Toxic fumes mitigation, dispersion, and reliability have improved “three to four times” since the contracts were awarded in 2022, he said. “The gun is done,” St John said.

He said the suppressor design was influenced by the SURG suppressor programme for Special Operations Command, which first identified toxic fumes as a problem, St John said.

On the NGSW programme, the company used computational flow dynamic software to be able to analyse multiple baffle designs at once, and used 3D printing technology to speed up the testing process.

“The old way of design would be: build three different designs, go and test them – whichever one works or got closer, let's improve upon that. It's a very slow process,” St John said. “With that flow dynamic software, we have the ability to map those gases for every single baffle design before we even bring it to the printer.”