The 10mm Auto was developed in the late 20th century as a compromise between the stopping power of the .45 and the velocity of smaller cartridges, and it spent about a hundred years being either forgotten or rediscovered depending on who was buying. By 2200 it's been rediscovered for good — the 'Combat Auto' loading is a full-power specification load standardized by the Arcturus Defense Solutions procurement office around 2170, producing a fast, heavy projectile that handles light body armor better than either the .45 or 9mm. The 'Combat' designation distinguishes it from reduced-power commercial loads that got popular after the original round's reputation for battering polymer frames became a logistical liability.

In GLMZ 2200, 10mm Combat Auto is the choice of people who want more than a service round but can't justify — or afford — the magnum revolver cartridges. Arcturus Civil Security issues it in some jurisdictions as a standard sidearm loading. Mid-tier enforcement contractors buy it by the case. Street-level operators who've been in enough situations to appreciate penetration over capacity run it in compact double-stack platforms and accept the magazine trade-off. Slagworks Industrial's ammunition division produces the dominant commercial load; Arcturus Defense Solutions produces a hotter contract load stamped with their triangle-and-star mark that costs significantly more and is technically export-restricted but shows up everywhere anyway.