Which portion of the projectile interacts with the lands and grooves within the bore to form an airtight seal and prevent gas leakage?

Which portion of the projectile interacts with the lands and grooves within the bore to form an airtight seal and prevent gas leakage?

• A. Eyebolt Lifting Plug
• B. Obturating band
• C. Rotating band
• D. Fuze Well

Answer: (B)

Gas seal is achieved through obturation. When the round is fired, the high gas pressure pushes on a soft obturating band that sits around the base of the projectile. This band deforms and expands enough to fill the tiny gaps between the lands and grooves in the bore, creating an airtight seal. That seal prevents escaping gases, so nearly all the energy drives the projectile forward rather than leaking around it, which also helps stabilize consistency and accuracy. The rotating band’s job is to engage the rifling to impart spin to the projectile; it sits in front of or around the obturating band but its main purpose is not sealing the bore. The other parts listed serve different functions—one houses the fuze, and the other is not involved in sealing the bore.

Gas seal is achieved through obturation. When the round is fired, the high gas pressure pushes on a soft obturating band that sits around the base of the projectile. This band deforms and expands enough to fill the tiny gaps between the lands and grooves in the bore, creating an airtight seal. That seal prevents escaping gases, so nearly all the energy drives the projectile forward rather than leaking around it, which also helps stabilize consistency and accuracy.

The rotating band’s job is to engage the rifling to impart spin to the projectile; it sits in front of or around the obturating band but its main purpose is not sealing the bore. The other parts listed serve different functions—one houses the fuze, and the other is not involved in sealing the bore.