Brass headspace question

[tlk]

I have some Rem brass that has been shot twice and didn't grow. 30-06. First was factory load, second was 56.5 gr of IMR4350. I am knocking out the primer before measuring with a with Lee Collet die, but only taking out the primer not resizing the neck. Measuring with Hornady Headspace guage - 2.035" head to datum line.

Did the brass not move or am I doing something wrong here with the die?

 

[britz]

I can only assume that is the optimum dimension of your chamber. If you can find some brass that is not resized and you have a sticky bolt lift check that headspace to the datum line and see the difference. I would suspect it to be a few thousandths longer.

 

[tlk]

Update and more confusion: I measured some once fired winchester brass and it is longer, with one case up to .003 longer than the Rem brass. There is no crush-fit with these longer cases either. These were also run through the collet die.

Since I am trying to work up a load I will neck size and increase the powder a half grain on both the Rem and WW brass, but I dont understand it. I thought all brass grew every time it was shot.

 

[boomtube]

Exactly what are you measuring, total case length or datum/headspace length?

 

[tlk]

Datum/headspace length.

 

[KRP]

Brass only "grows" when it is stretched so far that it can't spring back to its original dimensions. Lee collet die only sizes the neck, it doesn't touch the body. The Rem and WW case where probably different lengths to start with.

Bump the powder charge up if not stretching the brass is really a concern. If it is shooting up to your standards I wouldn't worry about it. Folks spend lots of time and money for tight chambers/custom dies/etc. to have brass that doesn't need, or only needs minimal, re-sizing.

 

[boomtube]

KRP says it correctly.

Case stretching is mostly an indication that we are over-resizing. Since your case shoulders aren't moving, they are fitted to match your chamber correctly. Neck sizing (especially with Lee's excellant collet sizers) largely prevents that stretching.

The only time you should see any total case length increase - stretching - is after you use your FL die to bump the shoulders back for better chambering. Excessively tight chambering effort IS harmful to best accuracy so the shoulders WILL need to be moved back slightly from time to time.