The rifle calibre issue is an interesting example of inefficiency since both were foisted on NATO by the USA.
Post-war, Western Europe was tending towards an intermediate-power 7mm round. The UK even issued it. But the US Army wouldn't accept a lower-power round so NATO soldiets suffered 7.62 Shoulder as a result. Until Vietnam, when the USA hastily adopted a fast but low-power varmint round.
After 50 years we're still carrying both calibres and no-one is happy, but NATO can't change unless the USA does.
Post-war, Western Europe was tending towards an intermediate-power 7mm round. The UK even issued it. But the US Army wouldn't accept a lower-power round so NATO soldiets suffered 7.62 Shoulder as a result. Until Vietnam, when the USA hastily adopted a fast but low-power varmint round.
After 50 years we're still carrying both calibres and no-one is happy, but NATO can't change unless the USA does.