The required velocity will ALWAYS be dependant on bullet construction.  Current M80 FMJ has plenty of velocity, but the thick bullet jacket prevents fragmentation.  Match bullets tend to have thinner jackets, and many of these WILL fragment in .308 as they do in .223 and other calibers.

Understanding this, it would certainly be possible to manufacture an FMJ load that fragments out to a given distance (the thinner the jacket, the less velocity is needed, and therefore the longer the fragmentation range from a given barrel length).

The only NATO .308 load known to fragment was the old West German ammo, which AFAIK is no longer manufactured.  It had a steel jacket, as a great deal of .308 does (including much US-made ammo), but the steel jacket was very thin, and was further weakened by the cannalure.  It seems that US Spec Ops folks figured out that the WG ammo was "much more effective" (not sure if they understood WHY), and apparently did their best to obtain WG .308 whenever possible.  I don't know the fragmentation velocity threshold of this load, but given that it no longer exists, the point is moot.

-Troy