A gun tube for a downhole perforating gun assembly includes a body having a cavity and one or more weights in the cavity. Gravity acts on the weights, which causes the tube body to rotate around its longitudinal axis so the weights are adjacent the lower part of the wellbore in which the gun assembly is positioned when oriented horizontally. This position shape charges in the gun tube in a desired position prior to the shape charges being fired. The gun tube may also include one or more end connectors with electrical contacts having a first, extended position, and a second, contracted position, and/or end connectors that can be assembled by hand without the use of tools.