The US Machine Gun Armory have developed a set of kits to convert the MK46 / M249 SAW into a range of 7.62mm calibers including the 7.62x39mm, 7.62x40mm Wilson Tactical, .300 AAC BLK and 7.62x51mm. All that is required is swapping out the top-cover, barrel and a few other parts.
The 7.62x40mm WT is available to purchase now for $866, with the rest of the kits going on sale after SHOT Show next year.