Abstract: A hydraulic cylinder projectile assures radial expansion of the projectile upon impact at low velocity with a target. A hydraulic cylinder insert is disposed in an axial central bore of a projectile body. The hydraulic cylinder insert has a closed leading end, and a compression ram element is disposed in the leading end of the insert. Liquid is disposed in the cylinder aft of the compression ram element. The hydraulic cylinder insert and projectile and the method of producing the same are described and claimed.