| Answer | Crossword Clue |
|---|---|
| CALIBRE | Diameter of a bullet. |
| CALIBER | Diameter of a gun bore |
| BORE | Inside diameter of a gun |
| BORE | Inside diameter, as of a gun |
| CALIBER | Diameter of the bore of a gun |
| CALIBRATE | Ascertain the diameter of, as a gun bore. |
| HOOP | Its diameter is roughly twice that of a basketball |
| FERMI | Unit of length that's roughly the diameter of a proton |
