Slug shooting requires higher pressures to move the additional weight and bearing surface that slugs have. In addition, with longer barrels, speed can be increased upon firing if the valve can remain open longer. Higher powers are achieved with a first-ever in the airgun world: the FX Tungsten Hammer Weight.
Tungsten is a material that is 1.7x denser than steel (used for the standard FX hammers). This extra weight hits the valve with more power which allows the valve to open even at higher regulated pressures and stay open longer
The Tungsten Hammer is instrumental with longer barrels (700mm & 800mm) as the longer the barrel, the more desirable it is to have the valve stay open (ideally to just before the slug leaves the barrel).
Tungsten Hammers is available for the FX Impact, Wildcat MkIII, FX Maverick, FX Crown MkII, and all FX Dreamline configurations. Note that those shooting standard pellets will not see benefits from the Tungsten Hammer.