What is the locking system for M4/M16?

What is the locking system for M4/M16?

• A. Tilting bolt
• B. Rotating bolt
• C. Locking lugs
• D. Falling block

Answer: (B)

Rotating bolt locking is used in M4/M16. The bolt head carries locking lugs that engage corresponding recesses in the barrel extension, and the bolt rotates to lock into place as the action cycles. A cam pin in the bolt carrier forces the bolt to rotate about 90 degrees during locking, creating a strong seal to contain the high-pressure cartridge. When the action cycles, the bolt unlocks by rotating back, allowing the bolt carrier to extract the spent case and chamber a new round after rotating to the locked position again on the next cycle. This rotating-bolt design provides a reliable, durable lockup for the rifle’s pressure. The other options describe different locking concepts not used in the M4/M16: a tilting bolt is a different mechanism found in some rifles, and a falling block is characteristic of single-shot designs. Locking lugs are the surfaces that actually lock, but the system is defined by the rotating bolt that engages them.

Rotating bolt locking is used in M4/M16. The bolt head carries locking lugs that engage corresponding recesses in the barrel extension, and the bolt rotates to lock into place as the action cycles. A cam pin in the bolt carrier forces the bolt to rotate about 90 degrees during locking, creating a strong seal to contain the high-pressure cartridge. When the action cycles, the bolt unlocks by rotating back, allowing the bolt carrier to extract the spent case and chamber a new round after rotating to the locked position again on the next cycle. This rotating-bolt design provides a reliable, durable lockup for the rifle’s pressure.

The other options describe different locking concepts not used in the M4/M16: a tilting bolt is a different mechanism found in some rifles, and a falling block is characteristic of single-shot designs. Locking lugs are the surfaces that actually lock, but the system is defined by the rotating bolt that engages them.