ORIGINAL: johnl if I were you i'd try to find a slug barrel I shot a slug out of my 500 and i ripped the barrel ( i had the mod choke in it ) the barrel ripped about 8 inches from the choke tube down
The Foster and Brenneke style slugs can be fired in ANY shot modern shotgun in good condition regardless of choke. They'll swage down, and safely pass through any degree of choke there is. Some other types might not, however!
As to Mod. 500 Mossbergs, half the southern tier shotgun-only deerhunters in NY use slugs in their Mossberg 500's. Most of them can't afford much more in the way of a shotgun, and I have never heard of one bursting a barrel IF THE BARREL DID NOT HAVE SOME SORT OF AN OBSTRUCTION IN IT!! I have also never heard that Mossberg says to NOT use slugs in their 500's!! This would come as a helluva surprise to a lot of people who have been using slugs in their 500's for the past 50 years or so!