In ongoing experiments at the Plasma Liner Experiment (PLX) facility at Los Alamos National Laboratory, two high Mach number plasma jets, composed of gases such as H and Ar, will be collided. We describe numerical simulations using particle-in-cell (PIC) and hybrid-PIC methods using the code Lsp. Using expected experimental plasma conditions (n ∼ 1014–1016 cm−3) large scale transport simulations demonstrate that the jets are essentially collisionless at the merge point. In smaller-scale 1D and 2D simulations we show that collisionless shocks are generated by the merging jets when immersed in applied magnetic fields (B ∼ 0.1–1 T). Unmagnetized collisionless shocks are not found in simulations at the expected jet velocities (10–100 km/s). Considerably higher velocities are required to see this effect. The orientation of the magnetic fields and the axial and transverse gradients of the jets are shown to a have strong