I did some reading and they say that you shouldn't shoot slugs through Full Choke barrels. But IC or Modified are fine, although you can damage the choke through excessive use of slugs. You only want to do it as a last resort so id say your safe i doing so if that situation arises.
Here's something i snagged off the web.
"As others have stated do not shoot slugs through a full choke. You can do it; but it’s very dangerous. It increases the pressures to dangerous levels. And it also causes metal fatigue. In other words you may get away with it several times then BOOM!
A full choke its good for tight patterns with bird shot and buck shot.
The slug may fit in the muzzle from a dissembled shell but that means little. You see when that slug takes off with soft lead it expands, (albeit slightly) but that little bit helps seal it against the .72 cal / 12 ga bore. The restriction of the full choke (less than bore) applies extreme pressure at that point.
And as far as accuracy is concerned it will suck.
UPDATE; I did some research on this question today. And if you are using Foster type slugs you can shoot them out of ANY choke barrel; "according" to the slug manufactures. But I got different answers from a gun manufacture.
Here is what Mossberg says;
http://www.mossberg.com/content.asp?ID=5…
“Can I shoot slugs or buckshot through a "smoothbore" field barrel with Accu-Choke™ tubes? (500/505/535/9200/88/930 models)
Yes, and with sabots or rifled slugs, the more "open" the choke tube, the better the accuracy ("Improved Cylinder" recommended.) The "full" or "modified" choke tubes are preferred for buckshot loads. Slugs, buckshot and steel shot loads are not recommended for use with an extra full "turkey tube" installed, due to the tube's tight constriction. Do not fire any load without a choke tube installed, doing so will damage the internal choke tube threads.
Can I fire slugs through my 935™ or 835® vent rib, Accu-Mag® choke tube barrel?
No, 935™ and 835® field barrels (those with a ventilated rib) are "overbored," and the extra inside diameter may cause the projectile to "wobble" producing unreliable accuracy. A projectile may wedge inside the barrel causing an obstruction. Obstructions of any kind can cause damage to the firearm resulting in damage to the barrel and/or personal injury to you or those around you. Dedicated fully rifled slug barrels are available for the 935™ and 835® models. Other 935™ and 835® Accu-Mag® choke tube notes: Buckshot and steel-shot loads are not recommended for use with an extra full turkey tube installed.
And this is what one slug manufacture has to say;
http://www.brennekeusa.com/web/text/faq.…
It seems some of their slugs can and some can not be shot thru a full choke.
And after searching the web; seems no one can agree on this.
Personally I will stick to not shooting slugs thru a full choke. Because years ago I watched a fellow shoot a slug through an old H&R Topper 12ga full choke and I could SEE the bulge of the slug travel down the barrel.
That was enough for me!"
At best from what I have read there are conflicting points of view. Some slug manufacturers like Brennke say you can shoot their slugs through a Full Choke. I have read a lot that says you should not.
Its up to you what you do. If your talking about Black Bears, just a shot in the air will prob scare them away anyhow.