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Old May 3, 2013, 06:30 PM   #5
Brian Pfleuger
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Join Date: June 25, 2008
Location: Central, Southern NY, USA
Posts: 18,298
Quote:
Originally Posted by mehavey
Problem #3 - Are you full length resizing? ... Sizing die all the way down to contact
the ram/case-holder, and then 1/16 turn more to overcome any flexing in the press?
I must take some exception with this instruction. While it matches the instructions that comes with most die sets and will likely make functional ammo, it is not best practice and is not good for best accuracy or brass life.

Properly full-length sized brass will have the shoulder "bumped" back between 1 and 2 thousandths of an inch from the maximum "as fired", unsized dimension.

To accomplish this, the reloader needs either the Hornady headspace gauge set or a bushing that is longer than the neck of the case and is the approximate diameter of the center of the shoulder:

Zero your calipers on the bushing and then measure the shoulder length of a bunch of fired, unsized cases. Better if they have been fired and neck-sized only 3 or 4 times. The longest ones are very close to your chamber dimensions.

You should adjust your sizing die to move the shoulder back no more than 0.002. Note that first the shoulder will actually grow longer, as the sides are squeezed and the shoulder has nowhere to go but up. As you adjust the die down, it will finally contact the shoulder and "bump" it back.

You need to make the adjustments in very small turns. Die threads are 14 thread pitch, which is 14 turns to the inch. That means that one full turn is 0.0714 and a quarter turn is 0.0178. Feeler gauges are helpful if you have them but trial and error works fine too, just takes a little longer.

Note that you're not really "bumping" the shoulder. The extra length is actually going into the neck... the case is getting longer. Be sure to check length after sizing and trim as necessary.
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Last edited by Brian Pfleuger; May 8, 2013 at 11:10 AM.
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