Originally Posted by OP/Jerry45
The LR and SM that I have, in BLUE boxes, are GM210M GM205M. Box says FEDERAL LARGE RIFLE MATCH PRIMERS then GM210M. Small Rifle same order of wording. I'm presuming the GM is for Gold Metal M for Match.
OK... you got me with a puzzle. I've never seen Federal Match in anything but the distinctive Red boxes.
As to differences between "Match" and "Ordinary," it's simply in the acceptance tolerances of the primer compound. In reality, the differences are very little (and sometimes the "ordinary" are more consistent in effect than the "match.")