Sig Sauer Inc. on Tuesday offered a first look at the automatic rifle and rifle prototypes for the U.S. Army's Next Generation Squad Weapon (NGSW) effort, after the service selected the company to advance to the next phase of testing for the 6.8mm weapon system.

Sig Sauer, maker of the Army's new Modular Handgun System, was selected recently along with General Dynamics-OTS Inc. and AAI Corporation Textron Systems to deliver prototypes of both the automatic rifle and rifle versions of the NGSW, as well as hundreds of thousands of rounds of special 6.8mm ammunition common to both weapons, to Army testers over the next 27 months.

The service plans to select a final design for both weapons from a single company in the first quarter of 2022 and begin replacing M4A1 carbines and M249 squad automatic weapons in an infantry brigade combat team in the first quarter of 2023, Army modernization officials have said.

As part of the NGSW effort, the Army tasked gunmakers to develop a common cartridge using the government-designed 6.8mm projectile.

Related: Army Picks Gunmakers for Next Test Phase of Future Infantry Weapons

Sig engineered a "completely new cartridge," resulting in a "more compact round, with increased velocity and accuracy, while delivering a substantial reduction in the weight of the ammunition," according to a Sept. 3 company news release.

The high-pressure, 6.8mm hybrid ammunition is a "significant leap forward in ammunition innovation, design and manufacturing," Ron Cohen, president and CEO of Sig, said in the release.

Sig's automatic-rifle version of the NGSW features a side-opening feed tray, increased available rail space for night vision and other accessories, and a folding buttstock. The rifle prototype features a free-floating, reinforced M-LOK handguard, side-charging handle, and fully ambidextrous controls, as well as a folding buttstock, according to the release.

Both prototypes will also feature a newly designed suppressor that "reduces harmful backflow and signature" during firing, the release states.

"The Sig Sauer NGSW-AR is lighter in weight, with dramatically less recoil than that currently in service, while our carbine for the NGSW-Rifle submission is built on the foundation of Sig Sauer weapons in service with the premier fighting forces across the globe," Cohen said in the release. "Both weapons are designed with features that will increase the capabilities of the soldier."

The new prototyping agreements call for each vendor to deliver 43 6.8mm NGSW automatic rifles and 53 NGSW rifles, as well as 845,000 rounds of 6.8mm ammunition, according to the original solicitation.

Textron announced Friday that it will lead a team that includes Heckler & Koch for its small-arms design, research and development, and manufacturing capabilities. It will work with Olin Winchester for its small-caliber ammunition production capabilities.

Textron Systems' rifle and auto-rifle prototypes will feature its signature case-telescoped ammunition technology developed under the Army's Light Weight Small Arms Technology effort over the last decade.

Read more: Textron Delivers Prototype for Army Next-Gen Squad Weapon

"The design features improved accuracy and greater muzzle velocity for increased performance, as well as weight savings of both weapon and ammunition over current Army systems," according to a recent Textron news release. "It also incorporates advanced suppressor technology to reduce the firing signature and improve controllability."

Textron is not releasing any images of its NGSW prototypes at this time but plans on showing off the weapon system at the Association of the United States Army's annual meeting in October, company spokeswoman Betania Magalhaes told Military.com.

Military.com reached out to General Dynamics OTS but did not receive a response by press time.

-- Matthew Cox can be reached at matthew.cox@military.com.