Hydra-Shok is a type of expanding bullet made by Federal Cartridge. It was originally patented by bullet designer Tom Burczynski. Hydra-Shok was debuted in 1988 after the FBI requested a bullet with better terminal ballistics than traditional cup and core projectiles. Hydra-Shok bullets feature a unique, patented center-post design and notched jacket with a non-bonded lead core. Together they are meant to provide more reliable expansion and deeper penetration than the other projectiles used at that time. Center post designed bullets like Hydra-Shok have more predictable results and therefore offer some advantage as a projectile. The manufacturer says that the scored jacket and center post design provide a "programmed" expansion. There has been much debate regarding the bullets unreliable expansion when fired through clothing or media other than ballistic gelatin. In ballistic gelatin, the bullet typically displays very rapid expansion resulting in a larger but more shallow wound channel than would be typical from most other bullet configurations in the same caliber and of similar weight.
The Hydra-Shok bullet is available in various calibers; 9 mm, 10 mm, .32 ACP, .380 ACP, .38 S&W Special, .357 Magnum, .40 S&W, .45 ACP, .45 GAP, and .44 Magnum. It can also be found in 12ga. shotgun slugs.