I have just heard about them and see this video of their effectiveness through some obstacles, looks like a good tool: non toxic except for targets
[youtube]http://www.youtube.com/watch?v=Um02l2SK6bU[/youtube]
I got too see these at the NRA version of Shot Show, in Pittsburgh, PA. They had a few that were "cut out" of the shell, or never loaded lol. They look really neat and the guy gave me a complementary box of the DDupleks Monolit 32 Slugs. I shot them out of my H&R Pardner Tracker II Slug Gun. Grouped pretty well! Approximately 1.5 - 2 inches at 75yards. Measured from Centers.
Kick was minimal for a 12 gauge. I never recovered any remains to say how much mass was retained from smashing through a 2x4 but holes were perfectly round. I'd say that a shoulder wouldn't stop these slugs!
EDIT: My H&R had a Fully Rifled Bore
Ddupleks also just came out with new Frangible Ammo!
I was actually considering them a replacement for Lightfield Slugs. I recent sold my ole H&R and replaced it with my current M500. So no more Rifled barrel and Brenneke don't shoot so well through thick brush with. The Black Magic Magnum 600 grain is a bit overkill but they get the job done! 495 grain and flat nose seems a bit more practical! They do have Magnum shells as well if you explore their site
EDIT: It would seem that from "Suitable also for rifled barrels" - They are primarily for smooth bore. Take it for what it's worth, but that is what I derive from that statement