Hi,
By the instruction book, Just unbolt the base at the bottom of the colomn and raise it, then tighten it at the upper position. If you are trying to reload 3-1/2" then you need a special kit. Call MEC for the right part number, but it will do 2-3/4" and 3." out of the box. Just make sure the dies are adjusted properly once you set the machine for the new size.
Manuals are available on line at MEC. FREE...
Paul