Interesting article.
http://www.policeone.com/police-prod...-at-SHOT-Show/
"The G2 bullet starts life the same way as the traditional Gold Dot bullet, as a lead core with an electrochemically-bonded copper jacket. A star-shaped punch is used to stab the bullet's nose and cut all the way through the jacket, forming stress risers. At the base of these cuts is a circular ring around the outside of the jacket that Speer engineers call the "hinge," whose purpose is to limit the amount of expansion as the petals of the bullet open up.
Interestingly, when the bullet is run through the final shaping dies, there is only a shallow dish of a cavity left in the nose. This dish is filled with liquid elastomer, which hardens as it cures. Upon bullet impact, this plug forces the bullet to open up along its star-shaped fissures and initiate the expansion that is limited by the hinge.
Since expansion is mechanically driven, and not hydrostatically driven (as it is on the standard Gold Dot), the G2 bullet performs more consistently after penetrating barriers, which can plug or deform open cavity designs and alter penetration depth.
In fact, Speer engineers tell me that penetration consistently reaches the 14 to 16 inch optimum range of the new FBI standards. This exceeds the typical 12 to 14 inch penetration achieved by the older Gold Dot, which was engineered to meet an earlier specification that could sometimes encourage shallower penetration.
The new G2 bullet will be loaded into nickel cases using low flash powders, and will initially be offered as a 147 grain 9mm, a 180 grain .40 S&W, and a 230 grain .45 ACP +P."