If you are using a Ponsness/Warren reloader, pay particular attention to the outside housing spring tension on the final crimp station. The tension on this particular spring affects how the crimp is closed. 

The spring needs to be adjusted so there is just enoungh tension to push the edges of the hull sufficiently closed before the center ram, which is fixed to the tooling die,  flattens the crimp closed.    If the spring has insufficient tension, a hole will be left in the exact center of the pie crimp.   Too much tension and the hull will develop creases.  

The spring tension also adjusts the tapering on the end of the hull. This taper, combined with the full-length resizing die found on Ponsness/Warren reloaders, helps the load chamber easily.

Ponsness/Warren reloaders have a very unique, and frustrating little trick, and you will never find it unless you know about it. Once you know about it, you will not let it stop you again.

At the final crimp station, there’s a chance that a little piece of plastic, sheared off of an old and crusty crimp will get lodged between the spring-loaded outside collar and the finish crimp ram. Once that happens, you will not be able to produce a crimp for love or money. To fix it, loosen the spring tension all the way, push the collar up manually, and extract the plastic bit or whatever may be jammed up in there, holding the collar out of position by a fraction of an inch.