The original NRA advice was based on .30-06 blanks being sometimes (often?) made out of rejected brass. That stuff just had a red laquer-covered cardboard in the case mouth, and a super-fast powder that was sometimes used in pineapple GRENADES!!!
U.S. 7.62 NATO blanks are another critter altogether, being purpose-built with that fakey bulletnose in the front. My official but dontchadaresuemeif'nI'mwrong recommendation would be to section a case first, make SURE the case neck is not too thick for safe bulletseating, and also make SURE no case thickness elsewhere is less than other USGI brass.
It would promise to be an ugly, labor-intensive task. Hey, where's the puke emoticon??