Depending on the type of bullets your loading a crimp may or may not be necessary.
If your using these in an auto loader, or a magnum type revolver, then yes you might want to use a crimp due to the bulet pull and the slamming action of the auto.
IF your simply using these in a bolt action, 99% of the time your spinning your wheels to add the crimp. You will also want to be sure your using bullets which have a cannalure on them as well. It is not a good thing to crimp slick sided bullets that have no groove as it distorts the jackets as well as pushes pressures up higher in your loads.
This said, to adjust your dies, you run all your bullets through the seater so that the groove is set to the lip of the case mouth. Then you back your seating stem out several turns, and then slowly adjust the die body down until the mouth of the case is crimped into the bullets groove. Your not looking for ti to be swedged into it, simply a nice roll over into it will suffice.
One thing on crimping, if you go there. I have seen way more loads that have been crimped too much than I have seen crimped too little. Most loads that need the crimped bullets, as mentioned above, usually need only enough to roll the leading edge of the case into the bottom portion of the groove. This is what holds the bullets in place under heavy recoil or fast motion. For handgun loads in auto loading pistols your looking for a taper crimp which simply preses the mouth tightly against the sides of the bullet. You have to be careful with these as well as a lot of these type rounds headspace on the case neck and you don't want to smash it so tightly that they miss this tiny shoulder.
If you do however decide you need to crimp your loads, I highly suggest picking up one of the Factory Crimp Dies to use as a stand alone process. This lets you go ahead with your loading as usual and not have to keep adjusting your seating die. Most literature and people will tell you that seating and crimping are best done in separate processes, and this is true, but on some of my revolver loads I have found that they shoot equally as well either way, and I usually seat and crimp in one motion, but there again, I am only putting enough crimp on them to roll the lip over into the bottom edge of the groove and hold the bullet in place along with the neck tension. This gives me the added amount of pull needed to hold them and enough added resistance to keep the slower powders operating at the pressure levels they need to burn.
Hope this helps, and it may or may not be the acceptable practices of everyone, but they have worked for me over the past 35+ years I have been loading.
