I have a 500 also and have hunted with it for about 10 years with slugs. I have the rifled BBL with the cantelevered scope mount.

Mine likes the federal sabot slugs and I choose to shoot the ones with the Barnes Copper hollow points.

Mine will outshoot many rifles at 115 yards (The longest I've shot it) and will group 3 shots into 3" at this range! I would have no problem taking a shot at 150 yds with this gun from a decent rest.

If you have tried the major brands and can't get at least a 5" group at 100yards, I'd have to say, you either have a really bad barrel or need to practice shooting with .22s for a while.

I'm not trying to be a smart @$$. I have seen plenty of grown men who have developed a bad flinch from heavy loads like slugs.