A modified coaxial plasma gun in the high density regime of 20-70 mT of He was investigated experimentally and theoretically. Tile injection of the plasma torus into a drift space was studied by diamagnetical diagnostics both with and without helical bias, where the inner electrode was continued into the drift space by an insulated central conductor. Quasi-tokamak geometry is obtained (q approximate to 3;I-i approximate to 1.2; beta(p) approximate to 0.7) Mean speed of torus in drift space: 2.2 cm/mu s, which is in excellent agreement with the MIID model derived. The theoretical considerations include: (1) acceleration phase, (2) ejection, (3) injection, (4) motion in the drift space, (5) tokamak stability. Discussion of: (1) general characteristics and phenomena, (2) second half-period breakdown with autopreionization (3) prevention of transversal expansion by rarefaction waves of Mach 50 supersonic flow, (4) stability and homogeneity enhancement (factor 5), (5) agreement with model, (G) X-points and breakdown dependence, (7) velocity limitation, (8) thermal diffusion. The findings are, among other application domains, important for future designs of injectors for magnetic confinement, especially for spheromaks.