Textron Systems NGSW Rifle and LMG

[stanc]

Case polymer wall thickness on CT is driving magazine bulk and linked ammunition volume as well.

There are three factors which determine CT cartridge diameter: Wall thickness; propellant space between the case wall and bullet; and bullet diameter.

Of those factors, the case wall thickness actually contributes the least to the cartridge diameter. The primary factor driving cartridge bulk is bullet size.

The bullet diameter determines the cartridge diameter, and the bullet length determines the cartridge length. Together they determine the magazine bulk.

An equivalent or even lighter 6.5mm with better BC would meet the armor defeat requirement.

Unfortunately, even if that's true, switching to 6.5mm would allow so little reduction in cartridge size, there would be no change in magazine bulk or capacity.