Might be a bit obscure if you've not come across the Pellucidar stories.
A cut-down version of a Lee Enfield short muzzle rifle, for use in confined spaces. Bigger clip to save reloading in the dark.
The uniform betrays the regiments cavalry history.
The motto on the badge reads "Attack from down under"
The pose is a bit stiff, and I may well revisit this if I get time and inspiration.