I've seen a few of these empties around, but mostly I think people buy them because they are a novelty. I've done some reloading with a roll crimper with shells that were 2" long and they seemed to work ok. They were your basic one ounce target loads. They weren't as significantly short as the Aguilas, but they were shorter than standard. I did it because the hulls that I used were already shot up (read as crimp was unusable) and I wanted to goof around. The idea of shooting these in a repeater seems that they might work for some guns and not for others. They might work ok in an 870 since the lift gate is not usually open like the Mossy is. Buy em and try em if you like. Standard shells work as well and if you need more ammo, buy an extended mag tube, if you can.
Vince