You are using the full length sizer for this.
The case(s) must be fire formed to your chamber.
You start with the sizing die set too long (high) by 1 full turn. You do this by setting your die normally with the ram and case holder against the die when the ram is all the way up and backing the die off by 1 full turn.
Lube your cases as you normally would
Run a case into the sizing die. Turn the sizing die down until it touches the case shoulder; you do this by feel. Some dies have flats cut in them (Lee) to ease turning the die. Some are knurled to do this with (Redding and RCBS are two examples) If you are having difficulty turning your die and feeling the shoulder, just keep moving the die down little by little until you bump the shoulder back. Use the method below to check your head space. If you over did it, back off your die a little and start with a different case.
Back down your ram and give your die 1/32 of a turn and run your case back into the die. This should be about right, but if you are getting a lot of case stretch, you may have to turn it a little more; bumping the shoulder back a little more. If you are adjusting and turning check the head space each time after making an adjustment.
Now check your case in the chamber, it should just fit. I mean it should be flush with the chamber mouth or just a .001" or .002" below in a break open gun. If the extractor is holding up the case, it should be removed during this adjustment period. If it does not hold up the case any, then it can be left in. If for some reason it does not have the proper head space adjust the die up or down 1/32 of a turn until you do have proper head space; using a different case if you went to far. If you do not have a depth gauge, use a straight edge across the chamber mouth and then feeler gauges between the case head and the straight edge to find out how much head space you have. Just make sure the case head is not above the chamber mouth. A human head hair is around .002" - .003" thick (no jokes about color or where
) 20 pound paper is around .004" thick. If you do not have feeler gauges, use a human hair and 20 pound paper. The hair should pull out from under the straight edge and the paper should not. You should not be below .003" for a good fit. It makes it easier to do this case fitting if the barrel is removed from the frame.
Lock every thing down so the next time you will have already properly set up for your cases for your chamber; remember it will be set for this one chamber only.
This can be used for any gun you want to just bump the shoulder back for a custom head spacing every time you reload. Usually with bolt actions, you do not have to do this every time, only once every third or fourth time ( it depends on how hot your loads are). In single break open guns, you may find you need to do this every time the case is reloaded.
After you are satisfied yu have the die all set, run another case in to verify your setting by checking head space again.
It sounds more complicated than it really is, just make your adjustments little by little and check after each adjustment. Good Luck and Good Shooting
