I don't shoot slugs for both cost and application reasons. Yes, Weevil is correct the Gun will shoot to a 1 o2 MOA accuracy at 100 yds., but you are very unlikely to shoot any pistol to that level of accuracy. I have hit crows and pigeons at 100 meters, but it's pretty much luck with a pistol. If you use a reflex sight, the dot is likely to exceed 6 inches at that distance. My GK1 is zeroed at 25 meters and I need about a 24 to 36 inch holdover at 100 meters. The biggest reason not to shoot slugs is the magazine's design. It is designed for Diabolo pellets. The magazine bore on my GK1 is exactly .250". Retension occurs because at the rear of each magazine bore there is slight chamfer and the skirt of the JSB pellets are .260" in diameter. It is the tail end of the pellet skirt that locks into that chamfer preventing the pellet from shifting forward and potentially jamming in the barrel. Most slugs are made via extruded lead wire. That process does not allow a shape that will lock into that chamfer. Slugs could be cast with a drive ring to lock into the chamfer, but none currently are commercially available.to my knowledge. If slugs were the option of choice, a redesigned magazine bore utilizing a slight forcing cone would solve the jamming issue similar to the Webley .455 pistol.
.Here’s a couple other good alternatives.