Brenneke makes an excellent 410 slug. The Brenneke 410 Silver Slug is a hybrid foster slug made of a relatively hard lead alloy with a trailing polymer gas seal and is one of the heaviest 410 slugs commercially available, weighing 114 grs. In my testing and experience hunting with them they perform very well.
Brenneke slugs will have in excess of 800ft-lbs of muzzle energy out of most 410 shotguns. The trailing gas seal design produces relatively good groups out of even tightly choke 410 shotguns and excellent groups out of open choked shotguns. Accuracy, IMHO, is a far bigger problem with most 410 shotgun/slug combination than the slug's terminal performance.
In terminal testing the Brenneke usually retains >90% of their mass. I have fired them into water jugs and wet phone books and in both cases they retain mass very well and get excellent penetration.
Below a picture of a terminal test I did on May 26, 2009. The targets were a line of plastic coffee container full of water. Each container is approximately 6 inches thick. The range was 25 yards for the test and the slugs were fired from a Stevens 38B bolt action 410 shotgun with a 22.5inch barrel. The muzzle velocity was measured that day at and average velocity of 1865.5fps. That would be 880.7 ft-lbs of muzzle energy. The Brenneke slug penetrated roughly 24 inches of water at 25 yards. The slug stopped against the back of the fourth jug leaving a noticeable impact on the side of the container. The recovered slug weight 106.3 gr (93% weight retention). As you can see in the picture despite the pop-off lids of the coffee canisters the slug manage to not only penetrate but split the first two contains.
For comparison I fired a 10mm round fired from a Smith and Wesson 610 revolver into the same jugs. The ammunition was a hand load that used a 180gr Hornady XTP bullet doing 1296FPS which produces 671ft-lbs of muzzle energy The velocity was chrono'ed during the penetration test. This certainly is not the hottest the 10mm can be loaded. There is commercial ammunition that will approach 750ft-lbs in a 10mm Auto but his is still a very substantial round and one many hunter might use for deer hunting. This 10mm load only managed to penetrate three of the same jugs and only split the first one.
I also did some wet catalog book tests similar to the test I did in my first slug testing. The results were similar and for a 410 slug impressive. The Brenneke Slugs penetrated 6+ inches of wet digi-key catalogs (very similar paper to a phone book). The weight retention was again very impressive with one slug weighing 110.9gr, 97% weight retension and the second slug weighing 113.9gr, 99.9% weight retention
Again I used my 10mm Auto and S&W; 610 revolver for comparison. At the same range and into identical catalogs I fired four 10mm rounds. The Hornady XTP bullet performed excellently. They mushroom beautifully. The penetrated ~4.5 inches of the wet catalog. Weight retention did fall off in this test with the following results. 1) 161.0gr (89.4%); 2) 148.5gr (82.5%); 3) 146.7gr (81.5%); 4) 142.3gr (79.1%)
Finally, real world experience. The buck I took two seasons ago was a roughly 180lbs live weight whitetail deer and was taken with Brenneke 410 Silver Slugs. The shot that stop him broke his back, shattering a vertebra and still exited the animal. From all my testing and use in the field the Brenneke Silver Slug is a tough and capable 410 slug. If you are willing to take the time to setup a accurate 410 slug gun and hunt within the relatively short effective range of a 410 slug (50-75yard for most setups) a 410 slug-gun with Brenneke Silver Slugs can be a great challenging way to hunt whitetail deer.