Abstract The mechanical description of the deceleration process of steel case fragments retained in CELOTEX ® panels in vertical mortar experiments is formulated. Ejected mortar fragments are classified according to their general shape into chunks and fingers and the corresponding probability distributions for linear momentum and weight are inferred. Mortar fragment momentum is beta distributed, whereas fragment weight is a Weibull variate. The equivalent pressure field and the resultant normal force exerted by a rain of flying mortar fragments on transverse panels are modeled. An example illustrates the application of the model using fragment information available either from experimental evidence or from simulation.