Sorry to revive this somewhat - what most are missing here is that Brenneke slugs (real ones) use a very hard lead in addition to the slug's design - they don't deform, pretty much ever. They run out of energy and are usually mostly intact after impact. For this reason, they don't lead barrels. As for the "penetrated 3 boards" stuff? Not Brenneke, I've never even seen a picture of a true Brenneke slug fall apart like that. Usually the only deformation you get is that the corners round off at the leading edge. Now the relevant question, one more time - where the hell are they???
Quote "I will do my own testing an come to my own conclusions. What some may not realize is that for WT deer, you don't need a slug that will over-penetrate. IMO energy transfer and massive upset puts deer on the ground. Also I've been useing Challengers for years out of both rifled and smooth barrel 870's and have put a pile of venison in my freezer. The leading from Challengers is nothing a copper brush and solvent can't clean and accuracy was never effected from leading."
Brenneke slugs are not a good choice for deer, they are absolutely the best defense against a charging Grizzly, or mature Black Bear, (or lightly armoured vehicle) that's trying to run you down. Very serious penetration, even through the skull of a bear, with slugs penetrating the full length of the animal having been seen.