308 Lapua brass keeps shrinking. Why?

[hkfan45]

I'm on my 9th firing of neck turned 308 Lapua brass. With every firing I notice that the COAL keeps shrinking, such that it is now below the minimum SAAMI length (it's now 1.995). This brass started it's life at 2.007. I full length size brass with a minimal shoulder bump of 0.0005" - 0.001". Questions:

Why does this brass continue to shrink? I thought brass was supposed to grow after every firing/sizing.

What can I do to stop the brass from shrinking? i.e. what am I doing wrong that is resulting in the brass shrinking?

Can I safely shoot this brass at below SAAMI COAL?

 

[nfhjr62]

Isn't there someone that ether works or is a Lapua supplier on this form, if he can't answer this than no one can??

 

[Jefferson]

wait a couple of days for an answer, :-*

Jeff

 

[hkfan45]

Forgot to mention my chamber length is 2.047.

 

[Phil]

Kevin Thomas is the Lapua Rep. on this site.

PM Him and ask him your questions.

Phil.

 

[mr45man]

I think if you measure your fired brass, then measure again after sizing you may get an idea what is going on.
John H.

 

[gotcha]

+1 for John H. Also, have you created a "knife edge" Chamfer? Or, over annealed so that bushing might be pushing the necks shorter? Maybe just too tight bushing.

 

[hkfan45]

I think if you measure your fired brass, then measure again after sizing you may get an idea what is going on.
John H.

I just did that and it seems that after sizing (bump of 0.001), the COAL goes from 1.995 to 1.997. So, the brass does grow slightly, but it still doesn't explain how the brass started at 2.007 and is now 1.997.

Also, can the brass be safely loaded at 1.997? Or is it too short?

 

[Ron IA]

your chamber is bigger so when you blow them out they get smaller check the OD mid way and by the start of the neck on a fired case and then a new one let us know what you see kinda think your fired case will be much bigger
Ron