as the bullet is propelled forward in the barrel it is not strictly necessary that corner 44a be rounded but it is advantageous to have both the forward and rearward corners of the liner segment rounded so that either end of any liner segment may face rearward this versatility simplifies the placement of the liner segments on a mandrel or in a mold prior to molding barrel exterior 12 around the liner segments in fig6 is a gun barrel 50 which incorporating modifications that can be made to gun barrel 10 the first modification is to the ceramic liner segments 46 which are also detailed in fig8 and 9 as with the first embodiment the liner segments together define a plurality of shallow spiralled rifling grooves or channels such as channel 48 and the sides of the segments are parallel to the channels the segments can form sharp ridges 54 or rounded ridges 56 however the boundaries between longitudinally adjacent liner segments are at the middle of the channels and not at the channel edges as in the first embodiment as bullet 58 passes through barrel 50 it forces segments 48 radially outward whereby gaps 52 between the segments are formed having the longitudinal sides of the segments at deepest part of the channels minimizes the depth of gaps 52 and thus minimizes blow by or undesired escape of p pressurized propellant behind bullet 58 it is contemplated that bullet 58 will be of a soft metal such as copper or a plastic such as nylon or polytetrafluorethylene another optional feature shown in the right half of fig6 is the presence of longitudinal reinforcing strands or fibers.