A shock mount device for a container includes a variable spring rate assembly coupled to a shock retainer. The variable spring rate assembly is removable from the shock retainer without removing equipment from the container. The variable spring rate assembly includes a replaceable core that may be exchanged with a replaceable core having either a larger or smaller durometer depending on a weight-to-load ration of equipment in the container. Removing and replacing the replaceable core may include removing and replacing the entire variable spring rate assembly.