The M400 features a direct impingement gas operating system, common to the traditional AR platform, with a rotating locking bolt.
Accurate, lightweight and crafted from the finest components, the SIGM400 Elite with optional ROMEO5 red dot sight sets the new standard for direct-impingement AR-15s.Learn More
M400 Elite Ti
Accurate, lightweight and crafted from the finest components and a titanium finish and optional ROMEO5 red dot sight, the SIGM400 Elite sets the new standard for direct-impingement AR-15s.Learn More
The First M4 to Earn the SIG Name.
We didn't set out to make just any M4. Instead, we used the innovation, performance and attention to detail that defines other SIG rifles to evolve the platform. The result is the SIGM400, a superior system offering advanced features available right out of the box that were once only found on the after-market.Browse Collection
Direct Impingement Gas System
After-Market Upgrades Made Standard
An extended charging handle latch allows for fast and easy access with optics mounted on the flat-top upper receiver. A built-in tensioning device eliminates accuracy-robbing play between upper and lower receivers.