A modular disruptor cannon includes three open-ended tubular structures. A first tubular housing defines a first interior region longitudinally aligned with a second interior region. The first tubular housing has external-surface threads at a first end thereof adjacent to the second interior region. A tubular insert is fitted in the second interior region. A second tubular housing defines a cap longitudinally aligned with a barrel. The barrel has an inside diameter equal to the inside diameter of the tubular insert. The cap has internal-surface threads for mating with the external-surface threads of the first tubular housing where the barrel is longitudinally aligned with the tubular insert.