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Old October 5, 2012, 11:36 AM   #1
jbondor
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Avoiding case stretching

I have tried several methods to prevent case stretching in resizing botlle neck cartridges; lubricating inside the neck, etc. I am now removing the depriming insert from the body of the resizing die and removing the primers with an old Lee "hit with a hammer" depriming tool. As a result, the case neck is resized smaller and is not enlarged by the withdrawal of the case from the die. I used a Lee case mouth expander to slightly bell the mouth of the case so it would accept the jacketed bullet, although needle nosed pliers would do just as well. This process seems to work fine, and I don't see any problem with it yet. I was wondering if any members do the same thing to avoid case stretching, or if any can see any difficulties doing this, other than a few extra steps in reloading.
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Old October 5, 2012, 12:37 PM   #2
Robert Palermo
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I seem to recall that RCBS came up with a series of X dies that was to prevent the stretching of the case when sized. That was some time ago and can't remember anymore than that but had read an article in that it actually worked. Don't even know if they still make them anymore.
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Old October 5, 2012, 05:42 PM   #3
Gster
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If you are reloading for the same gun all the time, your cases will last longer if you just neck size them.
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Old October 6, 2012, 04:49 AM   #4
1stmar
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Rifle or pistol? Rifle cases shouldn't be belled and pistol shouldn't need trimming or stretch.
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Old October 6, 2012, 07:27 AM   #5
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If you are encountering "case stretch," it's unlikely to be the expander ball** and more likely the sizing die being screwed down to far for the dimensions of the rifle's actual chambere dimensions.

If you are shooting a bolt action, try sizing only enough for the case to barely fit back in the chamber and the bolt close.

~~~~~~~~~~

** If the expanded ball is truly the problem, it will drag the shoulder forward as opposed to the causing classic case stretch. In either case, get a . http://www.midwayusa.com/product/547731/hornady-carbide-expander-spindle-assembly-for-rcbs-dies-219-zipper-222-223-22-250-remington-220-swift
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Old October 6, 2012, 07:28 AM   #6
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If you are encountering "case stretch," it's unlikely to be the expander ball** and more likely the sizing die being screwed down too far for the dimensions of the rifle's actual chamber.

If you are shooting a bolt action, try sizing only enough for the case to barely fit back in the chamber and the bolt close.

~~~~~~~~~~

** If the expander ball is truly the problem, it will tend to drag the shoulder forward as opposed to the causing classic case stretch. In either case, get a CARBIDE EXPANDER ball.

Last edited by mehavey; October 6, 2012 at 09:17 AM.
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Old October 6, 2012, 08:31 PM   #7
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The RCBS 'X' die works as long as you follow directions as far as case prep. I've been feeding my 7.62x51 gas guns from this die for over 15 reloads without any problems. The initial prep was a bit of a pain (about 1k milsurp brass), but smooth sailing since then. You can get some deformation if your expander is binding. Inside case neck lube (mica or graphite) can solve this as well as polishing the expander.
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Old October 7, 2012, 07:52 AM   #8
m&p45acp10+1
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If you are loading for a semi auto rifle case stretch is going to happen from what I have been lead to understand is that the stripping of the round some how stretches the case. Though I only load for .30 Carbine, and the cases are straight walled. They have not stretched at all.
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Old October 7, 2012, 08:04 AM   #9
Brian Pfleuger
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Lee collet die seems a lot easier.
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Old October 7, 2012, 10:51 AM   #10
243winxb
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Bottle Neck Cartridge

What you are doing is not expanding the case neck in the proper manor. Your bullet has become the expander, opening the case neck. This works at times, till the bullet seating stem leaves a ring on the bullet. It may take to much pressure to push the bullet into the undersize neck.

Last edited by 243winxb; October 7, 2012 at 04:14 PM.
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Old October 7, 2012, 11:13 AM   #11
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Quote:
I have tried several methods to prevent case stretching in resizing botlle neck cartridges
How do you know you have excessive case stretching? Have you experienced some case head separations?

Case stretching is caused by setting the shoulder back more than required to chamber properly in your rifle.

By their design, normal FL sizing dies, undersize the neck so the expander can enlarge it for proper neck tension when you seat the bullet. You can use a die like the Redding S die and by using the proper size bushing, you may not have to use an expander and still have the correct neck ID for your brass/bullet.

You can reduce the "force" required to withdraw the expander by either lubing the inside of the neck, using a carbide expander, or both.

But you haven't addressed neck runout. And your process may increased the run out of the neck and decreasing your accuracy.
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Old October 7, 2012, 11:26 AM   #12
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Does this problem tend to occur with belted cases? If yes, to the same extent, or less? Or is the belting irrelevant?
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Old October 7, 2012, 05:35 PM   #13
Clifford L. Hughes
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Most case neck stretching is from pulling the expander ball through the case neck. My method to deal with this is to polish the expander. After the polishing I clean the case necks with a bronze brush and then spray the inside of them with Hornady's one shot case lube. I usually get three to four loads before my cases need trimming.

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Old October 7, 2012, 06:30 PM   #14
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Too much fuss made over neck sizing.

If you neck size, you're still gonna need to FL size every so often anyway or your brass is gonna get too tight to chamber.

Properly set up to minimize shoulder bump, brass is not overworked and there are no "life expectancy" issues, and the need to trim is minimal.

I get at least 10 reloads outta my brass, and usually I retire them "just because" and not due to any warning signs.

This discussion is no different than barrel cleaning, break-in, and brass cleaning...everyone has their opinion, and swears to it.

I full-length size everytime, every caliber...JMO, YMMV...
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Old October 8, 2012, 10:59 AM   #15
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ditto/+1

tobnpr is dead on, don't try to make something difficult just because you can! William
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Old October 8, 2012, 10:10 PM   #16
Bart B.
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Normally, when a bottleneck case is fired, it gets shorter in overall length; the brass gets sucked back into the chamber as the case expands. Neck only sizing lengthens the neck (and therefore the case) a thousandth or so, but full length sizing lengthens the case more; the brass has to go someplace having been reduced in diameter. Having full length sized fired cases with both standard dies and dies not needing expander balls (same body dimensions in each die), how much they get longer with both methods is insignificant. This happens with both rimless and belted cases that headspace on their shoulders. New belted cases headspacing on their belts may get longer when fired if there's enough shoulder clearance when fired to allow it when the belt's hard against the chamber ridge and the shoulder's pushed forward against the chamber shoulder when fired.

Depending on how much the differences in dimensions of the chamber and case shortening amounts will differ when its fired. Measure case length before firing, after firing and again after sizing it to see how much its overall length changes. The more a fired case is sized with the die, the longer it gets.

In a case life test some years ago, I reloaded the same Federal .308 Win. brass case 47 times before running out of test powder. A full length sizing die was used with its neck lapped out to .335"; a couple thousandths smaller than a loaded round's neck diameter. The new, virgin case was trimmed to 2.000" when first loaded with a Fed. 210 primer, 42 grains of 4895 under a Sierra 165-gr. SBT bullet.

After its first firing, the case shortened about 4 thousandths. Full length sizing it to reduce body diameters about 2 thousandths an set the shoulder back the same amount, case length grew about 5 thousandths to just under 2.001". After 10 reloads, that case had grew to about 2.008" when it was trimmed back to 2.000". 10 reloads later, it had grew back to about 2.008". Same thing for the next 20 reloads. After the 47th time, it had grown to about 2.006". That case was never annealed.

A friend did the same test and his Federal .308 Win. case went 56 reloads before he ran out of IMR4064 under Sierra 168's. His load was fired in a match rifle clamped in a machine rest and put all shots in 1/3 inch at 100 yards. He didn't anneal his case either. His case had about the same case length change issues as he used the same type of full length sizing die as I did; I had lapped its neck out for him the same as my die had been modified.

Last edited by Bart B.; October 9, 2012 at 08:32 AM.
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Old October 9, 2012, 09:55 AM   #17
Brian Pfleuger
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Quote:
Originally Posted by William T. Watts
tobnpr is dead on, don't try to make something difficult just because you can! William
I see it the exact opposite. Full-length sizing, every case, every time IS making it more complicated than it has to be. Full-length sizing IS the complication.

I have cases that have been fired up to 8 times and NEVER been full-length sized, or trimmed. Neck sizing requires no lube, no cleaning off lube, just size and go. FAR less complicated than ALWAYS resizing.

The argument that you should do MORE work EVERY time because you'll EVENTUALLY have to do more work SOME TIME simply makes no sense to me.
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Old October 9, 2012, 11:58 AM   #18
89blazin
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IMO, the issue related to neck sizing vs. full length sizing is actually rifle dependent. FLS for semi autos, neck size for bolt, lever and most pumps.
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