I recently dissected a Strike-3 cartridge from a blister package and found that it was different from the type that I had previously known. Shown below are 2 types, one with a Winchester heastamp and copper-plated projectiles, the other has a Remington headstamp and unplated projectiles. Each of the copper-plated projectiles is about 3gr heavier than the unplated projectiles, and the total cartridge weight of the Winchester version is about 8.5gr heavier than the Remington version. I haven’t seen enough blister packs of this ammo to be sure, but perhaps most all of the Remington version is unplated, and the Winchester versions are plated projectiles?
Most all of the 15rd blister packs will have cartridges with slight cracks in the plastic projectile cap (as seen in the center above), while I assume the rectangular 10rd blister packs will show less or no cracking since the cartridges don’t rattle against each other in those. The opacity also varies in the plastic hull. Below are two of the R-P headstamp types from the same pack (darker on the right):