From NRA show, http://www.ddupleks-usa.com/
They have some impressive test videos
Their .410 DUPO-7 load was imported only once in 2011 - almost all by JG Sales in AZ I think, and in relatively small number. Apparently the advent of the .45 Colt / .410 Taurus Judge a few years earlier had sufficiently concerned some ATF attention for these as potential AP pistol ammo since the .410 slug was steel - like all Ddupleks loads, and they seemed destined to couple with the Judge. The fact that they were expanding slugs not intended to defeat anything more than hide / heavy-clothing and soft tissue was not relevant to the concern it seems.