not sure about the X, but think BR represents Bench Rest. Will not re-read the article in Hodgdons reloading magazine when powder reintroduced by company to make sure of what I'm about to write. Just recall there was a surplus powder 8208 once which was highly prized by benchrest/target shooters. Eventually, the supply of it was used up. Years later, a wealthy competition shooter wanting the powder again was willing to bankroll its production and contacted Hodgdon. Hodgdon, who had its beginning selling surplus military powder, doesn't make any powder, just buys it from powder manufacturers and markets it. Hodgdon discovered a powder very close to the original 8208 being made by ADI (?) in Australia. ADI supplies Hodgdon with a number of powders. Anyway, the ADI powder was renamed 8208XBR by Hodgdon and added to its line of powders.....think this was in 2010.