Headspace with full length resizing

[bgilli2]

I am struggling with setting my shoulders back the same exact demension every time. It varies by 5 thousands from piece to piece. I'll get two or three set back two thousands off fireform then next will be seven thousands for a few. Using rcbs rock chucked press and redding dies. This is for .30-06.

What would cause the shoulder not not set back the exact same each time and anyone else have trouble with this?

Thanks

 

[thethirdpig]

the differences are probably in the brass (the thickness at the base)

 

[Trental]

The only thing I can think of (as long as the dies are set up correctly) is that certain cases aren't springing back as much as others. How many times has the brass been fired?

What tools are you using to measure the shoulders? Good quality?

 

[boomtube]

"What would cause the shoulder not not set back the exact same each time and anyone else have trouble with this?"

They will never be 'exactly' the same for more than a few cases. Nor does it really matter with a factory rifle so long as the longest resized shoulder length doesn't exceed the longest fired lenght; that will insure the cartridges will all chamber smoothly and that's about as good as it gets. Only dead soft, totally over heated during annealing, cases will be totally mallible during firing and resizing.

The reason you see shoulder length (and diameter) variation is that the hardness/springback of cases does vary. It varies a little in the same new box and that hardness/springback increases each time you cycle them. The hardness variation acccounts for about half of the springing variation you're getting, the other half comes from your inconsistant lubing and final pressure and varying rythum when operating the press.

 

[bgilli2]

Thanks. I use good equipment. That explains why it is diiferent. The brass hasnt all been shot the same number of times. Probably why. Its a custom rifle and chamber. Just fyi....

 

[Trental]

Annealing the brass might get you better results, but that is another subject altogether.

I know Boomtube mentions that his brass never comes out the same but I don't find that to be the case with my resizing. Generally my brass comes out extremely consistent in headspace.

 

[ZSteinle]

What Happens To A Case

a very informative read and the end of the article has your name on it.

 

[bgilli2]

Thanks. Very technical article... So i am not that educated on this obviously. What am i doing wrong and what will fix it?

 

[boomtube]

"I know Boomtube mentions that his brass never comes out the same but I don't find that to be the case with my resizing. Generally my brass comes out extremely consistent in headspace."

Kindly note that I didn't even suggest mine don't come out very close to the same but I'm no longer a newbie. (I DID say that anal precision case lengths is meaningless for factory rifles.)

 

[ZSteinle]

i have never had a problem setting up my fl sizing die to over cam on the shell holder. but i have also never measured my cases off the shoulder after sizing. I would try that and measure them and see what you get.

 

[Trental]

Oh, I wasn't criticizing at all. Not at all. I was just putting out there my experiences.

Bgilli2, I wouldn't say that you are doing anything wrong necessarily. I do think that if you are mixing brass that you will have to expect certain variances in measurements after resizing. Do you have a lot of this brass that is of mixed number of firings?

Also... is this brass all of the same brand? If not, then there is no "fix".

Cheers!

 

[bgilli2]

Thanks. Very helpful. I appreciate the article and input. It's all nosler brass. I just have shot some 1 time and others 4 or 5 times... Bad practice I know. Would that do it? It's like I have to adjust the dies for each piece of brass. One doesn't set it back at all and the next will set back 7 thousands. I measure each piece with hornady headspace gauge after I resize. I want it one thousands off fireform.

 

[Trental]

IF this is what it is (work hardened brass)... every time you fire and resize a piece of brass you work harden it. Stretching and compressing the metal makes brass hard. It also changes it's "spring", meaning how much the brass springs back after firing or resizing. Your brass that has only been fired once is softer in the neck and shoulder area and is more malleable. The brass that has been fired 5 times is now harder and will have more spring to it, so as you... for a lack of a better word, squish it into the die and remove it the brass will "spring back" more than the once fired brass.

This is just my theory, and at this point it is only that... a theory. We need some guys in here with some other ideas.

To even all the brass back out you can anneal it (soften) with heat. I can give you a link to a gentleman that has an annealing machine that will clean and anneal your brass for a fair price. You ship it to him dirty and he decaps, cleans and anneals your brass and ships it back to you. Then you resize it and you should be golden. This will also prolong the overall life of your brass and reduce chances of split necks.

 

[LRSickle]

Here's something you might want to check. I FL size and set primers at the bottom of my stroke on many of my calibers. I was getting varying headspace measurements one time and found I wasn't seating my primers all the way and they were sitting proud of the headstamp surface a couple thou or so. Once I figured that out I either use a hand primer or check the primer with my thumb. Just a thought.