Sherman Bell's notes on hulls is located in post #48 here:
http://parkerguns.org/forums/showthr...?t=1092&page=5
He does not explain what OS stands for.
I have had no trouble crimping new unfired cut down hulls, either Rem or Fed using a MEC Versamec press. However if you experience a swirled crimp or some crushing stop and adjust the press.
http://www.ballisticproducts.com/bpi...ust/mecadj.htm