The troublesome problem of developing cusps in ordinary molecular wave functions can be avoided by working with momentum-space wavefunctions for these have no cusps. The need for continuum wavefunctions can be eliminated if one works with a hydrogenic basis set in Fock's projective momentum space. This basis set is the set of R$_4$ spherical harmonics and as a consequence one may obtain, solely by the ordinary angular momentum calculus, algebraic expressions for all the integrals required in the solution of the momentum space Schrodinger equation. A number of these integrals and a number of R$_4$ transformation coefficients are tabulated. The method is then applied to several simple united-atom and l.c.a.o. wavefunctions for H$^+_2$, and ground state energies and corrected wavefunctions are obtained. It is found in this numerical work that the method is most appropriate at internuclear distances some-what less than the equilibrium distance. In Fock's representation both l.c.a.o. and unitedatom approximations become exact as the internuclear distance approaches zero. The united-atom expansion can be viewed as an eigenvalue equation for the root-mean-square momentum, p$_0 = \surd(-2E)$. In the molecule, the matrix operator corresponding to p$_0$ is related to the operator for the united-atom by a sum of unitary transformations, one for each nucleus in the molecule.