Best method for checking for head separation?

[bigedp51]

Case stretching/separation is/are caused by excessive headspace in a rifle's chamber.

Biged's chart is interesting. I'd guess his gun does not have significant headspace. He didn't see failure for 7 firings. Ed, I'm curious to what you attribute the longevity of the lower listed cases? Brass hardness, wall thickness?

-West

Chambers and resizing dies vary in size, and each die needs to be adjusted for minimum shoulder bump. As an example I have a lee full length .223 die that will reduce the body diameter more than my RCBS small base die. And this same lee die can push the shoulder back more than any other .223 die I have.

Below shows head clearance of a cartridge and the amount of head clearance is directly related to how far you push the shoulder back during sizing. And the head clearance is how far the case has to stretch to contact the bolt face when fired.

Below shows what happens during full length resizing. And the main point here is only pushing the shoulder back .001 to .002 below the red dotted line. And when you push the shoulder back excessivly you are increasing the head clearance that allows the case to stretch and thin.

And to WestDivide's last question brass quality, hardness and wall thickness has a dirrect relation to case life. This and along with minimum shoulder bump extends case life.

Below I'm measuring a "FIRED" Lake City 5.56 case with my Hornady case gauge. I then adjust the shoulder bump for .003 for my AR15 rifle. And my point being if you measure your "FIRED" cases and set your dies up for minimum shoulder bump your cases will last a long time.

 

[Nevada Ed]

minimum shoulder bump extends case life. (post #21 )

True but if you just neck size for a bolt action..........
the brass will finally flow forward and you will notice that the bolt gets harder to close..........
and you will need to full size the brass case to where it is within spec's again.

Boy there are a lot of pictures of fancy instruments on this thread, that I never got in to , however there are a lot of serious shooters here in Reno that are into shooting clubs.

 

[pasote]

thank you

Chambers and resizing dies vary in size, and each die needs to be adjusted for minimum shoulder bump. As an example I have a lee full length .223 die that will reduce the body diameter more than my RCBS small base die. And this same lee die can push the shoulder back more than any other .223 die I have.

Below shows head clearance of a cartridge and the amount of head clearance is directly related to how far you push the shoulder back during sizing. And the head clearance is how far the case has to stretch to contact the bolt face when fired.

Below shows what happens during full length resizing. And the main point here is only pushing the shoulder back .001 to .002 below the red dotted line. And when you push the shoulder back excessivly you are increasing the head clearance that allows the case to stretch and thin.

And to WestDivide's last question brass quality, hardness and wall thickness has a dirrect relation to case life. This and along with minimum shoulder bump extends case life.

Below I'm measuring a "FIRED" Lake City 5.56 case with my Hornady case gauge. I then adjust the shoulder bump for .003 for my AR15 rifle. And my point being if you measure your "FIRED" cases and set your dies up for minimum shoulder bump your cases will last a long time.

Thank you for the information. I appreciate your help!
Ray

 

[Rule3]

Where and when did the graph of case hardness come from??
Brass can vary all over the place and different years or lot numbers. makes a big difference
The one 5.56 is from 2008 and the rest are 223. (yes technically there is a difference) Many brands are missing.