  We study scattering amplitudes of massive BPS states on the Coulomb branch of
$4d$ $\mathcal{N}=4$ super-Yang-Mills, utilising a little group covariant
on-shell superspace for massive particles. Super-BCFW recursion for massive
amplitudes is constructed and its validity is proven for all Coulomb branch
superamplitudes. We then determine the exact three-particle superamplitudes for
massive states. These ingredients allow us to explicitly compute the four- and
five-particle superamplitudes, which is the first non-trivial usage of BCFW
recursion for amplitudes with entirely massive external states. The manifest
little group covariance helps clarify both the role of special kinematic
properties of BPS states and the organizational structures of the
superamplitudes.
