case head expansion: too much?

[acrashb]

I just measured some unfired Lapua 223 cases and some fired ones (sample size of five each). The average difference: the heads on the fired ones grew .00072". I've read elsewhere that anything over .0003 is too much.

Should I be backing off two or three tenths?

 

[Canuck223]

I'd be more interested in how much they grew on the second firing after neck sizing.

 

['Boo]

I'd be more interested in how much they grew on the second firing after neck sizing.

Exactly.

The expansion on the first firing of virgin brass will always be greater than on subsequent firings.

 

[AKD]

when i buy once fired brass if its expanded so much its tight as hell getting it in the die i stop right there and throw it out. in a batch of 50 this might happen to like 2 rounds.

 

[Eagleye]

As Canuck223 and 'Boo said, the first firing of Virgin Brass is not the criteria to go by. It is subsequent firings that should show little, if any growth. Regards, Eagleye.

 

[acrashb]

Thanks guys, I'll measure the second firing and see how it looks.

This load is .2 down from a previous load that opened up the primer pockets in only five firings. Interestingly, with the previous load, the primer pocket uniformer took some brass out after every firing. With this load, no brass came out - just cleaned up the carbon.