Case stretch question

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pyscodog

Active member
My brass is new Nosler 280AI and my dies are new Hornady. I fired ten rounds of the new Nosler brass the other day and today started running them through my new die set. What I am noticing,is my once fired brass is coming out of the die .003 longer than it went in. I measure before resizing and measure after and it has grown/stretched .003. It didn't stretch the new unfired cases though. They come out the same size as they went in. I lubed the inside of the neck but still see .003 difference on all ten once fired cases. Is my decapping rod stretching my cases on the way out? If so, what do I do to stop this?

Note- I didn't clean my 10 fired cases before resizing. Could this be the problem?
 
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If your chamber is cut a little fatter than your FL die, when you size fired brass the die is squeezing down the brass to whatever dimensions the die is and when the brass gets squeezed down, it has to go somewhere and what you are describing is often the result. Can you screw your sizing die down any further or are you pretty well bottomed out?
 
New brass hasn't been fired and, thus, has not been stretched to fit the chamber. Sizing this case would do nothing to it's size.

With fired brass the die would size down the stretched case and the "extra" brass has to go somewhere. It flows up and makes the case longer. This is why you trim the case AFTER you size the case.

Case cleaning would have no effect. BUT, I would clean the cases before they go into a die. The slightest bit of dirt could scratch the cases and die.
 
Originally Posted By: marchboomNew brass hasn't been fired and, thus, has not been stretched to fit the chamber. Sizing this case would do nothing to it's size.

With fired brass the die would size down the stretched case and the "extra" brass has to go somewhere. It flows up and makes the case longer. This is why you trim the case AFTER you size the case.

Case cleaning would have no effect. BUT, I would clean the cases before they go into a die. The slightest bit of dirt could scratch the cases and die.



The cases were wiped off and lubed, I just didn't tumble them when I said I didn't clean the once fired brass. Maybe I should just shoot the new stuff then trim all to length before worrying about the extra .003 length. It just seemed odd that they came out longer than when they went in.
 
I highly doubt the neck length is changing. I'm sure you're gaining that 3 thou in body length.

Are you measuring the before and after at the shoulder or just the overall length, before and after? I'm guessing you're just measuring the overall case length.
 
Pysco, I think you’re worrying about a bunch of nothing. Brass grows. Here’s what I do... and I think about 99% of Precision shooters do the same thing or something very similar.

I don’t want any cam over on my first or second sizing, just screw it down to touch and back off 1/8 turn.

1) fire the cases
2) Measure the base to shoulder with a Sinclair gauge, and write down the average of 5 cases.
3) resize (try not to bump them at all but .001 is fine)
4) Fire the cases again.
5) measure base to shoulder again, and carefully set die to bump shoulders back .001-.002

If you anneal, do so before resizing.

Check your shoulder bump with each batch as annealing and work hardening can cause the shoulder to bump more or less, respectively.

Basically, I don’t take any measurements until after the second firing, except to make sure I don’t size excessively after the first firing.

Two loadings is usually enough for cases to form. Ackleys May take 3.

I also generally trim after the second firing just for uniformity, and I normally don’t do it again until 8-10 firings, with some exceptions.

You should absolutely have tools to measure shoulder bump and bullet BTO for every rifle you expect anything good from.
 
Originally Posted By: CZ527
You should absolutely have tools to measure shoulder bump and bullet BTO for every rifle you expect anything good from.

Yep.
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Like CZ says, brass grows, it's just part of the process, that's why we have to trim the cases every so often. They stretch out when you resize them. I always full length size NEW brass, but from there it depends on the rifle....
In any bolt or single shot rifles I generally get a Lee Collette neck sizing only die. This eliminates having to lube the brass at all. The brass expands to the size of the chamber after a couple firings and it fits like a glove. Once I start loading, I'll dry fit the first 5 or so rounds in the chamber. If it gets too tight at some point, and the bolt won't close or the action won't snap shut, then I'll F.L. size them and start over. I get excellent brass life doing it this way. I measure all rounds from base to Ogive for bolt and single shots.

With semi-autos and lever guns I always full length size. I buy a chamber gauge and check them that way. It will tell you if your shoulder needs bumped or the brass is too long. I always measure the COL of cartridges in semis and lever guns.
 


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