Same disingenuous NRA arse-covering as before. Enquiries at NRA and Proof Houses did not produce a shred of evidence to support this contention last time around. Note that the wording is still cut-and-paste from wherever they lifted it off the internet (Jersey Rifle Club c.1990s?).
The previous NRA assertion that modern ammunition was dangerous because it might be slightly larger diameter than older NATO types has been met with derision by most parties. Ironically, the main REAL issue has been target shooters building new state-of-the-art rifles with tight barrels and extremely short leads - i.e. conditions that simply do not exist in 40 year old Enfield barrels...
Its fairly irrelevant in any case: the NRA's issued target ammo (RUAG 7.62mm) now costs about 83p per round - I doubt any No4 target rifle owner is going to be blatting the stuff off in practice, let alone turning up at a top-level competition with an Envoy... (hmmm.... theres an idea for the summer...)