Caliber 9x19mm - Operating system Roller- delayed Blowback Proven reliable - Action Semi Auto - Barrel 8.86 3 Lug Nitride treated - Twist Rate 1/10 - Length 17.6 - Weight 5.05lbs - Trigger Pull 9-10 Lbs - Handguard Aluminum M-lok - Aluminum Picatinny Optic Rail - End Cap Black Polymer with Sling Swivel - Original Style Paddle Style and Push Button Mag Release - Magazine 30 Round accepts standard Milspec MP5 Magazines