It's not going away.
Despite all the back patting naysayers, where the 6.8 excels is with hunters wanting to use the AR in the field.
That means there's two issues - Hunters don't buy pallets of ammo, and they don't buy footlockers of magazines.
Most of the criticism expressed here is based on it not being able to compete price wise with the 5.56. Guess what, the 6.8 shooters who are dedicated to the round don't really care if it does. They can shoot 5.56 for cheap. 6.8 is for getting more power down range on LIVE targets.
Most of that is out to 350 yards, not because the cartridge is limited. After all, the 5.56 is supposedly effective to 500m, why wouldn't a bullet with a minimum of 30 more grains be less? That effective range limit is all about sightline distances in existing terrain, not a paperpunchers paradise of mowed grass. Hunting live targets that are naturally camoflaged and move with concealment in mind is the issue - not the cartridge. And picking one that doesn't have better ballistics inside the 350, just to extend it to 600m, is throwing your money away. Very few hunters shoot beyond 350m.
So what we have listed in the thread as complaints is that it's not cheap - well, it's not military surplus, duh. Neither are all the competitors mentioned. It's going to take firesale pricing to get the .300 down to $4.50 a box - that's the competition to meet, with the 5.56. If some don't see it being used in bolt guns or offered by a mainstream traditional gunmakers, again, duh. It's an AR15 alternate round built for that action - not Fudd ammo for a Fudd gun.
Claiming it's suffering because of the latest hot new round on the market? Goes to shooters easily swayed by what's cool, not what's effective. Sure, there's lots of press on the .300B0, but consider it's been out for over 25 years. It doesn't have the effective range to reach out to 350 and still carry 1000 foot pounds of force, it won't make the cut with American hunters. It's a short range, oversized bullet with a pinch of powder in a tiny case. You can't invent ballistics that make it superior with that.
There will be some who use it subsonic for hogs, but that means using a suppressor for best affect. Not many are so well heeled to kit out a AR15 with another $1000 extra for tax stamp and suppressor. It's a rich mans game, not a field hunter's.
6.8 dying? Our Academy just reopened after getting blown away by an EF5 last May, and guess what? They have Remington green box on the shelf, and the chain has carried Hornady in other locations over a year ago. 6.8 has shoved something else off with a superior sales track, something a retail chain cares a lot more about than "cool" factor. Only the top selling calibers get shelf space, it's about profit and turns. For a dying caliber, it's doing better than some other Fudd round that actually is going under. Not bad for a cartridge with limited application - it's an AR15 round and not much else shoots it.
Goes to - if you want to shoot the incredibly popular AR out in the field hunting, most are going 6.8. It's not 5.56 territory in some states, they still outlaw it. 5.56 has some distinct issues with the American hunter, it's a varmint round to them, not a medium game whitetail deer cartridge. To get an effective kill in an ethical manner, many have doubts, and don't care to use it. They buy a 6.8 and most of their questions get answered. It's not more expensive than .30-30, that stuff can run $5 a box MORE, and a few 5 or ten round mags aren't a major expense. It's all they have for their pistols anyway.
This exact topic thread pops up about every six months on a lot of other forums, it's pretty obvious it's an agenda to distribute misinformation and deceive the American consumer. It doesn't bother them if they get dirty slinging mud on the 6.8, as long as they can tarnish it's reputation.
If the ballistics match what you need done, use that specific cartridge in the gun it was designed for, and enjoy shooting it. But stirring up a storm to promote others because someone doesn't understand the application or how it's used is simply ugliness for it's own sake.