Remember that in the 1930s when John Garand was developing America's first semiauto service rifle, he had originally intended it for a 10-shot .276 cartridge that would have probably been an improvement over the 1906 cartridge design used in the M1903 Springfield rifle, itself in its third generation of cartridge and second major modification of rifle. But the stocks of leftover WWI ammunition were huge, and the financial conditions of the Great Depression dictated that we could have the new rifle, or the new ammunition, but not both, and then Army Chief of Staff Douglas MacArthur ordered that the new rifle be fielded in the same .30-06 ammunition as the M1903 Springfield, M1917 rifle, the B.A.R, and the .30 caliber machineguns. The war came, and MacArthur's decision proved to be a good one, and soldiers from Patton to priovate praised the Garand rifles they'd carried through that war. Half a decade later, the surprise of another war in Korea came to us, and the Garand proved still suitable in that conflict as well. And still it soldiers on today, here and there, as in Haiti, where it's recently had a part in another dictator's regime change.
If the 6,8x43 cartridge, not too dissimilar from the 7x44mm cartridge once proposed by the Danish Madsen firm proves to be more generally suitable than the 5,56mm, swell, we've again advanced the state of the art, and done a little more to give the American fighting man the best possible equipment with which to accomplish his task. If that cartridge changeover proves to be financially or technologically unsuitable, we can use the new rifle in the old cartridge chambering, maintaing the option of an eventual conversion *someday* if possible. And it's at least possible to changeover older M16/M16A1/M16A2/M4/AR15 rifles as well, should the new ammunition be an absolute success, as support and rear-area backwater troops have their capabilities enhanced, first with the new ammo, maybe eventually with the new weapons as well.
That looks like a win-win opportunity to me, well thought out and with fallback options if a part of the overall puzzle doesn't fit. My immediate respoonse has been to shop around for a few more AR15 lower receivers, at least one to be built up in the configuration with which I'm particularly familiar and fond of. The others may wind up in trim that conforms to the more recent thinking, or may not; we'll see how the Barrett and HKM4 upper receiver configurations work out in service. I'' be watching and listening carefully, but I don't at all consider myself locked into either the M16 platform or either the old 5,56mm or new 6,8mm ammunition.
It makes one wonder where we'd be if assault rifle development had continued on its original course (Fabrique Nationale's FAL, for example, was first developed around the 7.9mm Kurz cartridge). The Soviets settled on their version of the intermediate round and never looked back; but in the West, the bureaucracy resolutely dug in its heels and 7.62x51 NATO cartridge prevailed.
I appreciate the fine firearms which chamber the military .308 cartridge, but this 6.8mm round appears to hold much potential.
If the new cartridge is widely accepted, it may also bring with it another benefit: large supplies of milsurp 5.56 ammo for the civilian market. As nice as the 6.8mm cartridge might be, I doubt that we'll ever see cases of the stuff selling at gun shows before we're too old and feeble to drag ourselves out to the range. ;-)