In terms of historical precedent , it has also been a very ill advised tactic. From my reading , the following people had THIS to say about shotgun slugs :
1) John Pondoro Taylor mentions that in Ceylon , the men who made the largest bags of Elephant ( 1200 and 1500 , respectively ) used nothing but ordinary Smoothbore BREECH-LOADING shotguns of 12 and 16 gauge with the barrels cut down to 24 inches for general handiness. They used ordinary spherical lead balls . However , he also goes on to note that Ceylon Elephants were far easier to kill than African Elephant and that these weapons would never work in Africa.
2) Kenneth Anderson , in his book " Nine Man eaters and One rogue " makes mention of 6 different men who tried to use 12 gauge side by side shotguns loaded with slugs on Royal Bengal Tigers . Out of those six, some of them were killed. Some were horribly mauled. But NOT one actually succeeded in Bagging the tigers with the 12 gauge slugs. The slugs which they were using was called " Kynoch" lethal Ball.
Now , last year l DO recall reading an issue of " Field and stream " , where a gentleman used a 12 gauge Over Under Shotgun loading with 3 inch Magnum slug shells to kill an African Cape buffalo. He needed 3 shots to do it and found that the first two were broken inside the buffalo without penetrating the heart. I don't remember where the third shot hit the buffalo. It was either a neck shot or a third heart shot , which also had the slug break. But this time, the slug did have a fragment of it reach the Buffalo's heart. I will try to find the article and post it here