Russia? 5.45x39 in their AK-74, which ammo is also available in the States at really low prices. China? Their indigenous 5.8x42DBP, in their QBZ-97 bullpup.
With our proximity to China, the dearth of 7.62x39 is simply inexcusable. Would it have made better business sense for Twin Pines to import, er, truckloads of Chinese 7.62x39, that way their Chinese AKs and Czech VZ2000s will sell much faster?
"My garden is smaller than your Rome, but my pilum is harder than your sternum."