I don't believe there is any danger in using them but the rifling on the slug is different than the rifling in the barrel so the slug would have a tendency to jam as it is going through. I don't think is would make a block but the fouling from the lead would be very significant. I personally wouldn't use the slugs in that barrel. Get a smooth bore and enjoy.

Well, beleive it or not, I used to own a mossberg trophy slugster, and I shot the 1 oz activ slug through it. The acuraccy was excellent, and it never gave a problem. The bore did lead foul fast, but, heres the kicker...the more it fouled, the better it shot! probably because the grooves and lands were less pronounced. Keep in mind, that the pressure that a projectile travels down the bore under, that lead is liquid, and will conform to whatever surroundings it encounters.