It may be the most accurate standard-issue assault rifle in the world...
Lack of combat doesn't mean that something isn't better than the rest. The Ohio-class SSBNs are the most powerful and survivable weapons system in existence, but they've never been tested in war either...
ehhh that example is really pushing the limits of making examples.
the Sig 550 is a good rifle so i hear. ive heard it from lots of people actualy.
but, and this is a big but, almost no other nations in the world have adopted it in significant amounts. thats says to me that their are much better, cheaper, more reliable and more effective rifles available on the world market to field your nations military with.