Frank nailed it. Couple years ago, I got over on the SASS Wire and ordered my 45 Cowboy Special brass from a feller named Adirondack Jack. Seems Jack contracted with Star Line Brass to make up'em up. Case capacity is about the same as 45 ACP. Jack can provide all the loading data and details.
These cases are intended to work in guns chambered for 45 Colt. They allow for reduced loads, which can get a little squirrelly in the cavernous 45 Colt case, which was designed in the early 1870s for bulky BP loads. The Specials are great for use in old, fragile guns or any time you desire a reduced load in a gun chambered in 45 Colt and can be loaded on Dillon's progressive presses (maybe other progressives, as well).
The Auto Rim was introduced in the late teens or early twenties to work wiithout clips in the ACP-chambered guns of WW I. The Auto Rim case's rim is so thick the techs at Dillon say not even their engineers can figure out how to make'm run through Dillon's progressive presses. I load them on a single stage press and prefer them over ACPs in my 625, Brazilian, Pre-26 and Colt New Service revolvers for accuracy reasons.
Reason for edit: punctuation
I'm certainly no authority, but this is my "take" on the subject. Hope it helps.