stancrist said:

Assuming that the US follows through and fully fields the M5 and M250, I think the chances are good that -- as happened with 7.62x51 and 5.56x45 -- the 6.8x51 will be adopted by NATO. Especially if conversion of 7.62x51 machine guns to 6.8x51 is feasible.

The thing is a cartidge being adopted by NATO is not really a thing. It can get standardised by NATO. Which is simply a procedure. This is completly unrelated to a NATO member actually adopting it.
So even if the US military adopts the 6,8 and have it standardized by the NSO and get a STANAG it doesn't mean anybody else will adopt it. Especially not quickly. Far mor likely is that everyone will wait and see if the change is actually worth it and might concider a change in the next replacement program. Which might take decades. Its basically the same as it has been with 5,56. It took decades for all NATO countries to actually adopt the cartidge and weapons that use it.

stancrist said:

Actually, since Sweden not only is reportedly planning to replace their assault rifles with battle rifles, but has shown some interest in NGSW, I would rate Sweden (and perhaps Finland, which expects to replace its assault rifles fairly soon, and has partnered with Sweden on military rifle development and procurement) as being a "definite maybe" for adoption of 6.8x51

Very unlikely. The time frame is to short. Such programs move at a slow pace and future devlopments at the time of program start are not included. If the Swedes are allready in the process of evaluating and testing chances are zero that 6,8 will be included. They will finish their program and adopt a new 7,62.
For anybody to seriously concider 6,8 it would need to have a STANAG and be adopted and fielded by the US first. Befor the start of a program.

The German military also still technically is searching for a G36 replacement. Which as by requirement should be a platform solution for 5,56 and 7,62. 6,8 is not even talked about currently. So if Germany would finish this program and adopt a new rifle/rifles these would definetly not be in 6,8 and would last for at least a decade.

With the current situation in Europe small arms have moved to the end of the wish list again. IMHO its unlikely that any major NATO member would quickly change to 6,8.

njb3737 said:

I think Sweden is looking to start fielding a battle rifle some time in 2023 so maybe too soon for NGSW.

The build for the US army and the availability of ammunition will be a factor I believe against them taking it on at this stage.

It’s looking like a 7.62n rifle AR from Sako is the front runner on this ( others on this forum may know better ). In theory nothing stopping them from re barrelling to 6.8 in the future depending on the rifles design and any changes to the round.

I have not seen a planned timeframe for fielding.  If the Swedes want to begin fielding next year, then I agree that's maybe too soon for NGSW.

However, as per your final remark above, there is the possibility of switching to 6.8x51 at some point in the future.  From the article I linked to:

"...one thing that is being looked into is the possibility of having the new rifle being modular enough to allow for potentially changing calibre later – or even mid-production as the expected production run for any new assault rifle is expected to be measured in years – in case the 6.8 mm turn out to be a game changer."

mpopenker said:

       gatnerd said: I suspect 6.8 will appeal to those primarily concerned with China such as US and Australia.

one can wonder what kind of scenario this would be?

China invading mainland US? Seriously? Red Dawn, anyone?

China invading Australia?

Or both AU and US invading mainland China?

None of those seem plausible.

The Marines are planning a redux of their World War 2 "island hopping" campaign, with the Chinese cast in the role of the Japanese.

One potential location for a US vs China conflict is the one where they actually did fight a war 70 years ago:  The Korean peninsula.

stancrist said:

The Marines are planning a redux of their World War 2 "island hopping" campaign, with the Chinese cast in the role of the Japanese.

first you have to find such islands, and, second, that's a fast-track solution to the WW3, because China would obviously target supporting US carrier groups, and a loss of a major aircraft carrier for the US is hardly an acceptable price, unless a massive retaliation strike is offered immediately... and then - boom. nuke time.

schnuersi said:

IMHO its unlikely that any major NATO member would quickly change to 6,8.

I agree.  For that matter, I doubt that any NATO member -- major or minor -- would "quickly" change to 6.8x51.

mpopenker said:

that's a fast-track solution to the WW3, because China would obviously target supporting US carrier groups, and a loss of a major aircraft carrier for the US is hardly an acceptable price, unless a massive retaliation strike is offered immediately... and then - boom. nuke time.

Not necessarily.  They are clearly planning on conventional war, which seems to indicate that either they don't expect to lose a major aircraft carrier, or they're willing to take the loss if it occurs.

And -- depending on the scenario -- a major aircraft carrier might not even be involved.  An Amphibious Ready Group typically consists of three ships, none of which is a major aircraft carrier.

Reading between the lines, I get the impression that the concept is the Chinese try to seize islands to keep amphibious and carrier groups at bay, the Marines want to keep them from doing that. Then the Marines try to occupy islands closer to the mainland, to keep the Chinese from reinforcing any islands they are able to take.

As someone who has been following this technology very closely for a couple decades I can with great confidence tell you that the technology to pull these off well is more than here at this point.

I understand people's skepticism though. Thankfully a bunch of the key "see thru" display technologies this stuff has been waiting on have finally arrived and the cost on them is rapidly dropping.

This doesn't mean they can't still screw it up, it just means if they do it's because they did a bad job not because they're trying to overreach what's technically possible.

How should the NATO partners make any decisions regarding the new U.S. cartridge?

Nothing of substance beyond bullet diameter is known. Is it still 80000 psi?  Who knows. How are the severe practical problems following from using 80000 psi solved? Will it go down the drain like SPIW/SBR?  Is the goal of hitting body armour at 600 m (after all, you have to achieve a hit to penetrate) a realistic concept? Is such a requirement a healthy base for a new NATO cartridge? Is it still in effect? Open questions everywhere.     

In 1947,  when the British went over to proudly discuss the results of their so-called Ideal Calibre Panel with the U.S., they had absolutely no idea that  the U.S. already had been developing a new cartridge for around two years. We are beyond this stage, but not much. 

The islamists say "You need to know nothing beyond what is in the Koran." I am under the impression that the U.S. policy follows the rule that press statements about NGSW are all its NATO partners need to know.             

mpopenker said:

one can wonder what kind of scenario this would be? China invading mainland US? Seriously? Red Dawn, anyone? China invading Australia? Or both AU and US invading mainland China? What else could be there that would need a new small arms system

Well, Red Dawn seems to be making a comeback:

In terms of 6.8 fan fiction 

-Australia retaking the Soloman islands to prevent the establishment of a Chinese military base in their area, with Chinese and Australian Marines exchanging tungsten

https://www.aljazeera.com/news/2022/5/5/australia-urges-calm-after-solomons-leader-cites-invasion-claim

-China or US institute a Regime Change in the Philipines (to either break out or secure the first island chain), prompting the other side to try and counter it, either directly or through proxy. 

-US supports Japan to recapture the Senkaku islands from China

-My personal favorite - Vietnam attempts to achieve a security pact with the US, at which point China invades Vietnam to prevent US bases that close to its borders. In a perverse buddy movie, the US teams up with Communist Vietnam to fight Communist China. 

-And the most boring possibility - US sends ground forces to support Taiwan during an Invasion by China. 

...

That said, I'd place a lot more emphasis on Cruise Missile Submarines (like the 154 Tomahawk carrying Ohios) and long range Stealth Bombers with LRASM then I would on small arms.