Bonded core bullets normally retain from 75 to 100 percent of their weight after expanding, and can be more accurate in high acceleration loads because the core cannot slip or turn separately from the jacket.

 

Unlike solder, glue, or mechanical fastening, the diffusion bonding process creates a tensile strength gradient across the jacket/core boundry (rather than a sudden step or change in tensile strength). When subjected to high impact force, a boundry junction with an instant step change from the 6,000 or more psi tensile strength of the jacket into the 1,000 psi tensile strength of the core will tend to channel all the force into this area, causing the highest differential in stress to occur at the boundry layer.

 

The glued, mechanically bound, or soldered layer then acts like a stress riser, and peels the core away from the jacket because of the presence of a layer of oxide and carbonate on both the lead and the copper. The strength of a glued bond is always limited by the substrate or material to which it is fastened. No matter how strong the glue, all it can do is grip the oxide layer, which is peeled off under high stress. A diffusion zone lets the lead actually penetrate into the jacket, so that there is a smooth transition zone to move the stress into the lead core, causing it to peel back with the jacket when expansion occurs. 

 

Under an electron microscope, atoms of lead can be observed as deep as 3 microns into the jacket material after a few seconds of bonding time. Allowing the lead to penetrate into the copper provides a much stronger bond than is possible with any form of surface adhesive. Corbin Core Bond provides two actions to make this bonding possible. First, it removes the oxides and carbonates momentarily from both the lead and the copper, allowing pure metalic lead and pure metalic copper to be in contact with each other under elevated temperature. Second, it lowers the surface tension of the molten lead to allow the excited lead atoms to "wet" the surface of the copper rather than pulling back from it as the lead would do without the surfectant action, so that penetration can take place.