This paper presents the results of an experimental study of the elastic response of four geometrically scaled models of nuclear reactor outer containment shells to internal blast loading. The character of response of the shells to dynamic loading is determined with the shells unsupported (suspended in air) and with the shells half-buried in the ground. Geometrical modeling of the response is verified for both support conditions. The results of a static pressure test of one vessel show that dynamic response cannot be inferred from static considerations.