Yes they can shoot slugs. NSA and depending on caliber the Daystate Howlers. I have heard the Javelins don't work at all in them but that the Zan's did really well, according to one guy that called me up. I shoot different model Ghosts nearly every week and I've had enough time to try a few slugs here and there, but you have to be patient and test them out and see what works best. Each barrel is different, and so while one guy may have good luck with a specific slug the next won't. Try and repeat.
This gun is insanely powerful and awesome. Best of luck.