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When you guys talk about "bumping" the shoulder back, what does this mean and how do you do this?
[/ QUOTE ]Virtually all full-length sizing dies will set the fired case shoulder back from its fired position when the die's screwed far enough down into the press. Most die maker's instructions say to set the die to touch the shell holder with the ram all the way to the top then lock it in place. If the die's set too high, the fired case shoulder won't be pushed or "bumped" back far enough and such sized cases may be hard or impossible to chamber.
Best accuracy with full length sized cases typically happens when the case shoulder is set back .002- to .003-inches from its fired position. It take a shoulder headspace gage to measure this. Belted cases can have their shoulder set back twice that much as they should headspace on the belt, not the shoulder, for best accuracy.
When a case shoulder gage is used, the die can be set then locked in place for fired cases in a particular rifle chamber. A different chamber for the same cartridge may well have different shoulder headspace so the die would have to be reset.
When you guys talk about "bumping" the shoulder back, what does this mean and how do you do this?
[/ QUOTE ]Virtually all full-length sizing dies will set the fired case shoulder back from its fired position when the die's screwed far enough down into the press. Most die maker's instructions say to set the die to touch the shell holder with the ram all the way to the top then lock it in place. If the die's set too high, the fired case shoulder won't be pushed or "bumped" back far enough and such sized cases may be hard or impossible to chamber.
Best accuracy with full length sized cases typically happens when the case shoulder is set back .002- to .003-inches from its fired position. It take a shoulder headspace gage to measure this. Belted cases can have their shoulder set back twice that much as they should headspace on the belt, not the shoulder, for best accuracy.
When a case shoulder gage is used, the die can be set then locked in place for fired cases in a particular rifle chamber. A different chamber for the same cartridge may well have different shoulder headspace so the die would have to be reset.