why do the primers blow out on Fedral gold match 168 SMK in the H&K G3/91 and it's clones ? and yes the head space / bolt gap is in spec .017" and the same rifles have no problem with 7.62x51 nato surp Port,Hirt,Dag,Santa Barbra and Aussy. Is the GM308M brass too soft ? case wall thickness too thin? or do the primers have to be staked? even on my PTR-91 with the match barrel and chamber (early production sn # A0058) it happens . anyone else have this happen ?