  We solve for properties of $^6$Li in the ab initio No-Core Full Configuration
approach and we separately solve for its ground state and $J^{\pi}=2_{2}^{+}$
resonance with the Gamow Shell Model in the Berggren basis. We employ both the
JISP16 and chiral NNLO$_{opt}$ realistic nucleon-nucleon interactions and
investigate the ground state energy, excitation energies, point proton
root-mean-square radius and a suite of electroweak observables. We also extend
and test methods to extrapolate the ground state energy, point proton
root-mean-square radius, and electric quadrupole moment. We attain improved
estimates of these observables in the No-Core Full Configuration approach by
using basis spaces up through N$_{max}$=18 that enable more definitive
comparisons with experiment. Using the Density Matrix Renormalization Group
approach with the JISP16 interaction, we find that we can significantly improve
the convergence of the Gamow Shell Model treatment of the $^6$Li ground state
and $J^{\pi}=2_{2}^{+}$ resonance by adopting a natural orbital single-particle
basis.
