caliber

例句：

1. 1. The rifle was caliber 20 and it was very accurate.
   这把步枪的口径是20毫米，非常精准。
2. 2.The gunsmith measured the barrel of the gun to ensure it was of the correct caliber.
   枪匠测量了枪管的口径以确保它是正确的。
3. 3. The accuracy of this new caliber is unmatched in its class.
   这种新口径的准确性在同类中无与伦比。