As some explained FMJ (full metal Jacketed) Bullets are not legal to hunt with for big Game in many jurisdictions because they don't expand as well as non FMJ Bullets. However, I cant remember ever seeing a .303 FMJ Bullet loaded in Shells unless they where Military Surplus and I would be surprised if CT sells Military Surplus Ammo. Could it be the Clerk at the CT Store was mistaken in his assessment what kind of Bullets where loaded in the Shells he figured was FMJ, you bet that is a real possibility.
Cheers