Case head separation
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J E Custom
Well-Known Member
Normally it is to much head space, or the cases have been over sized. (Causing the same problem)
J E CUSTOM
Pardon my ignorance, but you're referring to bumping the shoulders back too far? If so, how much do you like to set them back?
Schnyd112
Well-Known Member
We had a guy separate a case at a competition on Saturday. Not one other issue with ammo aside from the one case and it completely separated. He had trouble opening the bolt, then just the head popped out. He tipped it up and the rest of the case fell out.
It was (I believe) once fired, .308 lake city brass. Could one have been short from the start? Maybe it wasn't noticed because the sizing die never touched the shoulder? All of his brass was sized by the same operation.
It was (I believe) once fired, .308 lake city brass. Could one have been short from the start? Maybe it wasn't noticed because the sizing die never touched the shoulder? All of his brass was sized by the same operation.
.001-.002".
Is this a belted magnum? If you full length resize them all the way then what you described will often happen.
It's a 270 Win. Bolt lift is easy, primer edges are still rounded, and no marks on the head of the case.
This is the only rifle I've had problems with.
bigedp51
Well-Known Member
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If you have a Hornady cartridge case headspace gauge you measure the fired case and adjust the die for minimum shoulder bump.
Reloading dies and chambers vary in diameter and headspace length. And setting up the die per the dies instructions can over resize the case.
When you bump the shoulder back .002 when sizing, the chambered cartridge will have .002 head clearance. The further you push the shoulder back the more head clearance you create and the further the case can stretch when fired.
The reason they say to only bump the shoulder back .001 to .002 is this is within the elastic limits of the brass and the case should not stretch and thin.
Below if the die is not adjusted low enough the case can end up longer than the chamber at the blue dotted line.
When the die is properly adjusted the shoulder will be pushed/bumped .001 to .002 below the red dotted line.
When the die is adjusted per the dies instructions it can excessively push the case shoulder back and create excessive head clearance. This excessive head clearance allows the case to stretch and thin in the base web area when fired.
Example, I have a Lee .223 die when setup per the instructions and making hard contact with the shell holder. The die will push the case shoulder back .009 shorter than a GO gauge and create .010 to .011 head clearance. This same die will reduce the case diameter "more" than a small base die will.
Bottom line, your dies can be adjusted for a custom fit to your chamber and not over resize the case.
Reloading dies and chambers vary in diameter and headspace length. And setting up the die per the dies instructions can over resize the case.
When you bump the shoulder back .002 when sizing, the chambered cartridge will have .002 head clearance. The further you push the shoulder back the more head clearance you create and the further the case can stretch when fired.
The reason they say to only bump the shoulder back .001 to .002 is this is within the elastic limits of the brass and the case should not stretch and thin.
Below if the die is not adjusted low enough the case can end up longer than the chamber at the blue dotted line.
When the die is properly adjusted the shoulder will be pushed/bumped .001 to .002 below the red dotted line.
When the die is adjusted per the dies instructions it can excessively push the case shoulder back and create excessive head clearance. This excessive head clearance allows the case to stretch and thin in the base web area when fired.
Example, I have a Lee .223 die when setup per the instructions and making hard contact with the shell holder. The die will push the case shoulder back .009 shorter than a GO gauge and create .010 to .011 head clearance. This same die will reduce the case diameter "more" than a small base die will.
Bottom line, your dies can be adjusted for a custom fit to your chamber and not over resize the case.
D
Deleted member 25294
Guest
If you have a Hornady cartridge case headspace gauge you measure the fired case and adjust the die for minimum shoulder bump.
Reloading dies and chambers vary in diameter and headspace length. And setting up the die per the dies instructions can over resize the case.
When you bump the shoulder back .002 when sizing, the chambered cartridge will have .002 head clearance. The further you push the shoulder back the more head clearance you create and the further the case can stretch when fired.
The reason they say to only bump the shoulder back .001 to .002 is this is within the elastic limits of the brass and the case should not stretch and thin.
Below if the die is not adjusted low enough the case can end up longer than the chamber at the blue dotted line.
When the die is properly adjusted the shoulder will be pushed/bumped .001 to .002 below the red dotted line.
When the die is adjusted per the dies instructions it can excessively push the case shoulder back and create excessive head clearance. This excessive head clearance allows the case to stretch and thin in the base web area when fired.
Example, I have a Lee .223 die when setup per the instructions and making hard contact with the shell holder. The die will push the case shoulder back .009 shorter than a GO gauge and create .010 to .011 head clearance. This same die will reduce the case diameter "more" than a small base die will.
Bottom line, your dies can be adjusted for a custom fit to your chamber and not over resize the case.
I noticed with a set of RCBS FL dies that I have to give it another 1/2 turn downward after touching the shell holder, otherwise the bolt will close really hard on the sized case.
I arrived at the additional 1/2 turn method by turning the die down in small increments until the case would chamber easily.
Do you suppose this is a bad method of determining shoulder bump?
J E Custom
Well-Known Member
Head space is set by the Gunsmith to allow loaded rounds to be chambered. Head space can be anywhere from .000 to .003 thousandths over the SAMME head space go gauge depending on the use and need.
Once a round is fired in the chamber only the minimum sizing is recommended for best brass life and loading. Some rifles (Semi Autos) need to be full length sized to function properly.
Bumping a shoulder is no different than under sizing a round buy full length sizing in that It increases the effective head space. Bumping the shoulder can cause problems If the Reloader does
not have a head space gauge or have years of experience. I recommend a minimum sizing no matter which method is used just to get the loaded round to chamber.
A Field no go gauge will usually be between .006 and .008 thousandth longer than a go gauge and if the bolt will close on a field (No Go) gauge, It is considered unsafe and has to much head space.
Best brass life and accuracy Is obtained with no head space .000 and most accuracy gunsmiths will head space between .0005 and .0015 and depend on the owner to properly size there brass when loading. Factory headspace is normally around .003 to .004 (The maximum recommended) in order to fire all brands of ammo and make chambering easy, With no consideration for brass life and accuracy. (They just want it to function).
I don't own a bump die because I have not needed one and fit the sized case to the chamber with
no bolt slack. (The bolt will close and has no head space). I also do not shoot over pressure loads
that will require heavy bolt lift for many reasons. Over sizing and working the brass leads to short brass life.
Just the way I load.
J E CUSTOM
Jerry M
Well-Known Member
If you have a Hornady cartridge case headspace gauge you measure the fired case and adjust the die for minimum shoulder bump.
Reloading dies and chambers vary in diameter and headspace length. And setting up the die per the dies instructions can over resize the case.
When you bump the shoulder back .002 when sizing, the chambered cartridge will have .002 head clearance. The further you push the shoulder back the more head clearance you create and the further the case can stretch when fired.
The reason they say to only bump the shoulder back .001 to .002 is this is within the elastic limits of the brass and the case should not stretch and thin.
Below if the die is not adjusted low enough the case can end up longer than the chamber at the blue dotted line.
When the die is properly adjusted the shoulder will be pushed/bumped .001 to .002 below the red dotted line.
When the die is adjusted per the dies instructions it can excessively push the case shoulder back and create excessive head clearance. This excessive head clearance allows the case to stretch and thin in the base web area when fired.
Example, I have a Lee .223 die when setup per the instructions and making hard contact with the shell holder. The die will push the case shoulder back .009 shorter than a GO gauge and create .010 to .011 head clearance. This same die will reduce the case diameter "more" than a small base die will.
Bottom line, your dies can be adjusted for a custom fit to your chamber and not over resize the case.
Great illustrations.
bigedp51
Well-Known Member
- Joined
- Dec 10, 2010
- Messages
- 1,022
Rifle chambers and dies vary in diameter and cartridge headspace length. Sometimes you may need to lap the top of the shell holder and sometimes the die never touches the shell holder for correct shoulder bump. Redding competition shell holders push the case from .002 to .010 "LESS" into the die than a standard shell holder. This is because the deck height of these shell holders are "LOWER" than standard. Another method would be to use feeler gauges between the shell holder and die for less shoulder bump.
I have a Lee .223 die if adjusted as you describe above the shoulder would be pushed back .010 to .011 shorter than the chamber headspace.
The main reason they say to only bump the shoulder back .001 to .002 is because this is within the elastic limits of the brass. Meaning the brass can stretch to meet the bolt face and then spring back without stressing and thinning the brass.
