Complex sentence: The results of the NATO tests were analyzed by a group formed of experts from Canada, France, the United Kingdom, and the United States, and the group's conclusion was that the 5.7 × 28mm was "undoubtedly" the more efficient cartridge.
Split into simpler sentences: The results of the NATO tests were analyzed by a group formed of experts from Canada, France, the United Kingdom and the United States. The group's conclusion was that the 5.7 × 28mm was "undoubtedly" the more efficient cartridge.