AR-15 5.56 16" STAINLESS STEEL BULL BARREL X-TREME FLUTED 1-9

 Here is a breakdown of the key features mentioned in the description:

• Material: The barrel is made from 416 stainless steel, which is a common material used in firearms manufacturing due to its strength and corrosion resistance.
• Hardness: The barrel has been hardened to a Rockwell hardness (rc) of 26-32, which indicates its ability to resist deformation and wear.
• Twist rate: The barrel has a twist rate of 1-9, which refers to the rate at which the rifling in the barrel rotates the bullet as it travels down the barrel.
• Grooves: The barrel has 6 grooves, which refers to the number of spiral grooves cut into the inside of the barrel to impart spin to the bullet.
• Gas block: The barrel has a diameter of .936" under the gas block, which is likely the location where the gas from firing the cartridge is tapped off to cycle the firearm's action.
• Gas system: The barrel has a carbine length gas system, which is a specific configuration of gas port placement and length that is designed to function optimally with certain types of firearms.
• Crown: The barrel has a target crown, which is a specific type of barrel end that is designed to improve accuracy by reducing the amount of gas turbulence that occurs as the bullet exits the barrel.
• Extension: The barrel comes with a barrel extension and extension pin installed, which are components that allow the barrel to be securely mounted in the firearm's receiver.
• Feedramps: The barrel extension has M4 feedramps, which are specific angled cuts that help guide the cartridge into the chamber of the firearm.