StevieB, the 3000 was advertised as a replacement for the 870 because of its ability to overcome a shell back condtion.It was a blatant imitation of the 870. But...
The drill you describe is the clearance drill for the 870.I first learned of this at an instructor's school in 1981, At that point I had been using 870s for over 20 years and didn't know they could have a shell back condition.For those that missed the several times I've mentioned this here, check the Archives.Be advised it's for emergencies. Pieces of stock get knocked off sometimes. For un-crises, make the weapon safe and dismantle the magazine to remove the errant shell through the front of the mag tube.
The 3000 was used for less than three years, when the remainder of those not returned to S&W were surplussed. They didn't hold up to being ignored, abused, neglected and misused like the 870 did. Civilians have little idea of how duty weapons are treated,by administrative and personnel lackadaisicality and ignorance.
I've an idea that if kept clean and lubed, used by those who were tender in their care, the 3000 would have made a better showing.
And, contrary to Urban Myth, the Flextab slot in the carrier was not to allow access to a stuck shell, but to FLEX enough to allow an errant shell to function.It worked, tho at this point the only glitches I've had with ANY 870 were deliberately induced.I believe my lifetime total may be around 50K rounds through divers 870s....