It CAN work that way- it's how I test Mosin Nagants and .22" rf rifles- find the maker and lot of ammo that the particular weapon likes.
However, the FNM seems to be about as good as it gets w/ std surplus ammo- it's pretty much at least acceptable (generally rather better, though) in anything you care to test of the appropriate caliber. Some standard (non-match) rifles won't group any better even w/ match ammo.
Major downside these days- its Berdan primed, so no reloading. Upside is- you don't worry about losing empties!
ETA- If you want the single LEAST "precise"(accurate) NATO 7.62x51 in my experience?: Get some US M80 ammo- you'll wonder how your rifle became a "shotgun" all of a sudden! However it IS reloadable and reliable- good for short range CQB work and belt feds.