Requirements for Replacement of Currently Issued 5.56 M-855 and 7.62 M-80.

[stanc]

4. To replace the 7.62x51 a new cartridge needs to achieve the following:
- to equal the barrier penetration performance of the 7.62mm M80 in terms of overall penetration of a range of media...

How about using 6.5x55 as sort of a surrogate for your proposed round, and conduct barrier penetration tests with it versus 7.62 M80? That way you can get some hard data (at relatively low cost) to validate the theory that your intermediate round can actually equal 7.62 penetration.

Norma markets 6.5x55 ammo loaded with the 120gr FMJ, and IIRC other companies offer 139gr loadings. And on your side of the Atlantic, it might even be possible to get mil surplus AP?