What is going on??!!

[cecztayl]

Hey guys. First let me apologize if this has been brought up already. I cruise this sight day and night since I've become a member and don't recall seeing this brought up....and I'm freaking frustrated lol.
So, my problem. I purchased some new dies a little over a month ago, because I would think the quality of these would be better than what I was previously using. With the F-L die I set it up to bump my shoulder back to 1.621 (.308 win) which should set my should back roughly .002-.0025". So I size several casing (14 in this instance) and everything is perfect then all of a sudden on case #15 my measurements are coming out at 1.630-1.627....WTF. So I simmer down and pull the die apart and clean it out leaving the lock ring in place so everything will go back to the same as close as possible. Still showing the longer readings!! I'm using unique case lube. I've tried less lube, more lube, no lube at all on neck and shoulder (which gave the most consistent readings for those 1st 14 cases, when before while very lightly lubing the necks I would see sometimes a .001" variance, this method had no more than a .0005" variance). Then all of a sudden everything goes to shit! This has happened a few times and I've tried eliminating anything I might be doing to cause this but I'm pretty freaking OCD with being consistent and can't figure out where this much variance has come from when my procedure has not changed. Any advice is greatly appreciated.

 

[ChrisGarrett]

If you have no lube built up inside, it's quite possible that your 'correctly' sized cases were actually short to begin with. Not all brass 'springs back' to the same extent as the previous case, or the case being fired after.

Did you measure them before you sized them? What are you using to measure case headspace, the Hornady HS gages? Are you measuring them right out of the chamber?

Sometimes, I'll size some older Lapua/Norma 338LM brass and I'll actually increase headspace after sizing, whether with a FL die, or a body die. It's like the body width has to go somewhere and that's causing things to lengthen.

How are your cases coming out of your chamber, vis-a-vis body width? If you have a wide chamber, this might cause the cases to grow longer, as you squeeze that body back down to SAAMI specs.

Just guessing here.

Chris

 

[cecztayl]

Thanks for the reply Chris!!
Yes using the hornady H-S gauge.

H-S Measurement on all cases in this session measured 1.6225"-1.623 after firing from my rifle/before sizing.

Body width after firing/before sizing:
.457" right below neck
.463" mid length
.469" bottom
After sizing:
.450" right below neck
.458" mid length
.466" bottom

Yes, after sizing my case length usually grows. But have just recently noticed the issue in the H-S measurement to shoulder. Usually that growth will be transferred to the actual case length which then requires trimming.

But like you said with your 338 my head space is all of a sudden growing .009" when several cases prior were perfect.

 

[rocketron]

did you run case #16 before you took the die apart? running # 16 would tell you if the problem was that pice of brass or the set up.

 

[cecztayl]

Rocketron, yes I went through case number 24 and they all had the same issue.

I may have found an answer to my problem or part of an answer to my proble..stupid me for not thinking of this first.
This brass is once fired from 2 friends of mine. Hornady&LC 13 brass fired from a bolt action(group 1) and some more LC 13 brass fired from an AR-10 (group 2).
Now, this brass was previously FL sized and has now been fired through my rifle and the issue arose after fire forming and then trying to size to my specs.
What I have narrowed down is the brass that had the longer headspace after sizing was the brass from group 2 all the brass from group 1 was consistent with my goal measurement.
I have sized all the group 1 brass and now I am going to adjust the die and re size all the group 2 brass to my specs and fire again to see if the same issue continues.

 

[witchhunter]

Segregate your brass and only use one headstamp, whatever you have the most of. Keep your brass separate for each rifle, this will simplify your loading headaches.

 

[cecztayl]

Witchhunter, i do keep everything separated. These 2 groups of 12 casings were separated by head stamp and loaded in 2 separate ladder test with everything else being the same. I was comparing pressure signs and velocity between the 2 headstamps to see what kind of difference I would see. I was also using this to fire form