I seem to remember browsing through our old test data when Altoona was still DOJ/INS. The 40 was only required to penetrate the 8-9" or whatever. But that was also the 155gr stuff. Later, when we switched to the 180gr, I think Altoona bumped the penetration up to the 12" requirement.
Also I think the shallow penetration requirement was bare gel alone and was probably more to see how well a bullet might expand and stay together. That's just a guess but we're talking 1995 or 1996 time frame. There weren't some of the durable barrier blind bullets around back then that we may take for granted nowadays.
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