Haven't read through all the threads, noticed that Cappy on YT had some info up about this. Isn't this some kind of back to the future kind of scenario? Thinking about the Swedish and Japanese 6.x ammunition. Between 7.62 and 5.56. Note that I have not drilled down to the specifics of the aforementioned ammo vs the current ammo. Back in the day, in my post Vietnam service in the Australian Army, there was intense discussion regarding the SLR and its 7.62 ammo, yes, heavy, but super reliable, easy to maintain. Anything hit with it wasn't getting up again. It was also recognized that 5.56 had its advantages also, M16, lightweight, could carry plenty of beans. To that end, at section level, our M60s were 7.62, section commanders, scouts carried the M16, No 1 rifleman carried the M203, the rest carried SLRs. Note the multiplicity of ammo types. Typical of the loadout from Vietnam days. From what I can make out, there wasn't too many dramas re logistics. Discussion in the boozer revolved around the merits of said arrangement, certainly the best of both worlds.
The Swedish ammo would come up as something in-between, perhaps a viable replacement for 7.62 and 5.56? With current situation, with the 6.8mm "winning" isnt there a hint of the 1950s situation, where the .280 round was preferred, however standardization with USA won the day, along the lines of "you will all now use 7.62"...to again be turned on its head in the '60s with the adoption of the 5.56 as the standard? I cannot see militaries, particularly a relatively small military like Australia, suddenly going oh, yes, we will have that..anytime soon. Just my five cents worth (we dont have 2 cent coins anymore).