Speculation on my part, but it looks like Sig may be covering all possible options with the upcoming US Army carbine competition. Their “M400” is a standard AR with a gas tube. Mentioned in the video is a modified extractor – I’d like more details on this. Beyond what you see here, I have no information about this weapon.
Curious that they don’t just promote their other systems (516 and 550 series) as being superior. I guess Sig finally figured out that not everyone is drinking the gas-piston Kool-aid?
*slow clap* Good job Sig, you have restored some of my faith. Guess they realized the 516 wasn’t as innovated as they thought, and deiced on giving the end user options instead of just a gas piston ala Ruger.