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

[stanc]

As Joe pointed out, the requirements do not specify that the existing gun designs in which the round is to be usable have to be those sized for 5.56mm - in fact, I believe that would be an unhelpful restriction.

I am thinking more in terms of the FN SCAR H and MK48 LMG as being the kind of guns which this could be suited for.

I see. When you wrote, "The cartridge designs should be optimised for use in conventional military magazine-fed and belt-fed automatic weapons, so that existing gun designs can be adapted to use them," I didn't realize you were referring to only two existing weapons.

Yes, the Mk17 rifle and Mk48 machine gun should be easily adaptable to a new, longer cartridge. It seems like that will incur significant penalties in weight and bulk, though.

I think if I were to opt for a longer cartridge, while still keeping minimum size and weight of both guns and ammo, I'd consider resurrecting the 1970's 6x45mm SAW round.