I used to buy solid lead 12 bore rounds called polycore in Canada. from 50 metres a polycore round would blast its way through and through a heavy duty galvanised steel armcor culvert. Never got to fire them at anything living though.
I remember seeing solid shot shells on sale in France, allegedly used on wild boar, I wouldn't want to use them with any shotgun that had choked barrels for fear of bursting them!!
Ok another myth busting moment, shotguns with full chokes should be fine to fire solid shot out unless the cartridge packaging says otherwise. Many slugs are only effective in fully choked bores. The damage to barrels is more likely to result from them being shot out or having small imperfections during manufacture. I cast and load slugs, the one and a half ounce Lyman Shocker slug for the 12 bore is designed to be fired from a full choke using a full length plas wad/shot cup. This is because the slug is actually 20 bore and being designed like an ounce and a half eley wasp airgun pellet will fit well and its skirt will expand to fit the bore should it part company with the wad/cup before leaving the muzzle!
I have had some astonishing accuracy out of these and I find that hollow base slugs shoot better than solid base ones.
I fired some solid slug in the USA many moons ago from an Ithaca 12 gauge, the rounds were rifled and hollow point and made one hell of a mess of a tree from 30 yards. I have one of the rounds that was cut from the shell somewhere, if i can find it ill post a pic. Camm1