Any change over, in any of our uniformed armed forces branches let alone all of the branches in the (DoD) Department of Defense, or NATO the armed forces of Europe, is always a huge undertaking.
Just coordinating the budgeting, and the bureaucracy, let alone the actual logistics of distribution of any new item like ammunition.
That whole NATO thing this like trying to turn a super tanker ship vs. a jet sky that can turn on a dime.
The tanker takes miles to maneuver.
So, does NATO compared to a USN SEAL TEAM.
Anything fielded in NATO takes time, maybe a year or more,but they have done it, and can do it again, eventually.
In a war time emergency they can speed up, and expedite that process.
In peace time that can drag it out more. But, itās doable.
They have fielded new armored vehicles, and new aircraft many times, as well as ammunition.
Itās just that the M-16 and 5.56 cal, or .223mm ammo has been around since the late 1950s, going on six to seven decades, and also involves changing to the weapons chambered to the new ammunition, including the distribution of those weapons, and training the troops on them too.
Not just shipping out crates of a new caliber ammunition to all the units that will replace the old ammunition saying here you go use this now, but in what also.
That has to be distributed also.
That is a much bigger challenge to accomplish that is significantly more complicated in its totality.
But, like new armored vehicles and and new aircraft means training drivers and pilots, and maintenance crews also how to keep the new equipment functional.
Armorer in armories have to lean the new weapons also, inspect, clean, do function checks, and needed gun smithing to keep the new weapons functional too.
In addition to supporting the new caliber ammunition. Itās a big undertaking.
The easy part is that all the jobs in all those services have skills transferrable, and can adapt to recalibrating to the newer 6.8mm replacing the old 5.56mm ammunition.
With the new weapons that ammo feeds is an additional layer of logistics, and education to go with it.