Originally Posted by Canadian Bushman
Im not arguing this. This is true for every press with any die.
Im saying creating more resistance as the press cams over by screwing the die down more, is not necessarily pushing the case further into the die.
This is not true and it is beside the point i was trying to make.
Some cases, when being sized in a particular die, do not need the die to contact the shell holder in order to have the headspace bumped back enough to properly chamber in the rifle they are being sized for.
If you set up your die by contacting it to the shell holder, there is a good chance you could be overworking the case.
The "CAM" is the most upward part of the stroke of your press's arbor.
When you reach this point the press handle is moving the greatest distance relative to the distance traveled by the arbor. You always want to run through this point on any press operation because it assures your arbor is reaching its highest point with the greatest amount of force. This is regardless of the amount play you have in your arbor or its alignment to the die. If the seat is contacting the bottom of the die at this point and you are feeling resistance in the handle, chances are the case is as far into the die as it will be able to go.
In my opinion screwing the die down any further is only stressing the components of your press. You would benefit more from running the case through the die a second time or even removing material from the base of the die or the top of the shell holder, than you would by screwing the die down any further.
SOP for me. You'll find all my dies to be ground on the base and/or the shellholder. Issue is, the base and/or shellholder has to be ground square to the ram axis or they will contact in a skewed manner. No big deal here, I fixture them in a surface grinder and grind them that way. Just a couple thousands, no more (depending on the shoulder bump according to my headspace gage.
If the die is manufactured to SAMMI specification, an interference fit between the die base and the shellholder will almost always bump the shoulder back too far and overwork the brass and in the interests of longevity of cases, you want to bump as little as possible. You have to determine the headspace required and then bump back a couple thousands, no more. The easiest way is to use a fired case and measure the shoulder datum with a repeatable fixture. I use a Hornady gage myself. However, keep in mind that each chamber is different, just like fingerprints, so the fired case must come from the chamber you want to size for....
All dies will set back the shoulder on a bottleneck case when resizing, don't matter if the die is a fixed cavity or a bushing style, bushing style being a better choice for neck tension and you can remove the bushing and expander ball for bumping without sizing.
I run both ways depending on caliber and end use. Smaller calibers like 223 aren't so critical as the internal dimensions are smaller so a fixed cavity will work fine. On larger calibers (3 series and larger), bushing dies are the way to go because the internal dimensions of the die are larger and more room for error.