Can you use shells that have been star crimped for roll crimping? I hope this isn't a dumb question.....I really don't know anything about it. Where can I get good instruction as to how to? Thanks.
Previously fold crimped shells do not work well, however, if you trim a quarter inch off the end you get rid of most of the crimp and you will get much better results.
There are a number of posts on roll crimping posted on 16ga.com some using old time hand operated crimpers which I prefer and others using a variety of drill press mounted crimpers. You will also find a hull trimmer that you can make for less then a dollar that works better than anything on the market.
Good luck.