Som Bang sier så er 40 cm anbefalt lengde på morter til 3"...
Krutt mengde anbefalt for 3 " er da 1 oz (ca 28 g), men helt opp til 1 1/2 oz (42 g) kan brukes vist det skal være andre ting i bomben som kanskje store kometer og lignende. Krutte som brukes er 2FA (4-12 mesh = ca 4,5mm - 1,7 mm granulat)...

"A rule of thumb frequently used for lift charge calculation is one ounce of 2FA for every pound of shell weight up to 10 lbs, and 1/2 oz of lift for each pound in excess of 10 lbs. The larger the shell is, the more factors such as mortar length, shell length and shell clearance come into play."

Source: Pyrotechnica IX


"The mortar length is measured from above the bottom plug. A rule of thumb is 5 times the mortar diameter for shells under 8 inches, and 4 times the mortar diameter for shells 8 inches and up."

Source: Illustrated Dictionary of Pyrotechnics