As you assemble high performance shotshells you will find that crimp depths can vary, even to a point where it is difficult to make a proper fold crimp. A compromised crimp will compromise the combustion process, reducing performance significantly. High Performance loads vary shell to shell because components such as slugs, buckshot and rigid hunting wads, by their nature, are not flexible platforms. Roll crimps adjust to the load, (instead of the load adjusting to the crimp) and the results are more consistent & sustained combustion and improved performance, critical for long-range accuracy. Roll crimpers can be used with a hand drill or drill press.