.308 Headspace Question

[tnichols]

I've just started reloading for my GAP10. I have only reloaded rifle ammo for my bolt guns in the past (neck sizing only). So, for the gasser we have to full length size. So, I'm using once fired Winchester brass from SWA that has been run through the GAP10. I have been measuring headspace with an RCBS Mic. My understanding is that the RCBS Mic "0" is set to read minimum headspace. So, through some reverse engineering and measuring, both SWA and Black Hills Match (using 175 SMK's) is running .002-.003 under minimum headspace. So, I set my FL Forster sizer to give me .003 under. Here is the question. I end up with about 70% of the brass perfect. A few end up .004-.006 under and some others on top end are right at min or even .001 over min headspace. Are the ones that are .004-.006 under safe? Can they be used for foulers, under 300 yd. stuff, etc... The few that end up "long" (min to .001 over) what do I do with those? I've run them through 2X with no more set back than the first time (spring back?) Am I doing something wrong? Enlighten me.

Specifics:

Once fired Win brass.
Dillon 550 with Forester FL sizer.
Hornady One Shot Lube.


I'll be glad to provide more details if needed.

Thanks fella's.

 

[ChrisGarrett]

Remember, even though we reloaders deal in really small amounts, lengths and measurements, nothing's perfect. You brass cases might have different amounts of work hardening and some will spring back more and some will spring back less.

Also, if you started out with a case that had shorter HS from the factory, that case might not have stretched consistently and filled out the chamber, so it's left with a shorter length to the datum line.

A piece of typical printer paper is about .0035" thick, so if you're keeping things to +/- .001", that's pretty damn insignificant and pretty darned good.

The ones that are way under, if that measurement is correct, will stretch and eventually you're get some case head seperation and have to trash them. Nothing you can do if they're not filling out the chamber, except shoot them until they die.

Chris

 

[tnichols]

Thanks for the reply Chris. I figured the ones in the .004-.006 range would eventually have a case head seperation if I continued to set them back that far. On the few that are at min or .001 over, would you just run 'em OR wait till the end of the run, and then turn down the die just a touch to get the desired amount of shoulder bump? Thanks.