From personal experience (I worked at Hercules before it became Alliant), if the canister powder's name is the same, so will be the ballistic performance. Canister propellants made for sale to hand loaders are blended to produce very similar ballistics performance forever even though the formulation may have changed slightly. i.e., barring any degradation due to age or poor storage, Bullseye or Unique made in 1920 will perform very similar to performance of the same powders made last week. That does not mean that reloading recipes remain constant forever.