Definition
Calibre is the inside diameter of the tube that fires the device, given in millimetres in Europe (in inches in the United States: 3", 4", 6"). It describes shells, mines, candles and the tubes of cakes. Common values run from 20 to 30 mm for cakes, 50 to 75 mm for small display calibres, 100 to 150 mm for large municipal shows, and 200 to 300 mm for major events. Calibre governs everything else: burst height and diameter, lift charge, net explosive mass, the mortar to be used and the distance to be kept from the audience. Common French guidance holds that each millimetre of calibre calls for roughly one metre of safety distance, unless the manufacturer specifies a stricter figure.
In practice, for the display company
Calibre is the first field on a product sheet: it determines the mortar reserved, the distance computed for the safety perimeter and the size of the burst rendered in PyroSimulator. PyroDesk sorts stock by calibre, refuses a shell in an undersized mortar and totals net explosive content per calibre for the declaration.