The Weibull unimodal distribution satisfactorily describes only those cylinder fragment spectra produced from brittle steel explosively loaded by high-brisance explosives. To describe the bimodal spectra obtained from the loading of ductile steel cylinders by TNT charges and other low-brisance explosives, we propose a statistical model of the spectrum in the form of the hyperweibull distribution function. We establish an excellent agreement between the proposed model and experimental spectra of steel cylinder fragments.