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Old January 6, 2013, 08:55 PM   #1
blackhawk8
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Neck Sizing question

All my dies are FL sizing dies, if I want to neck size only do I have to have a special die. Thanks for the help
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Old January 7, 2013, 12:30 AM   #2
the led farmer
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Yes
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Old January 7, 2013, 12:46 AM   #3
Ifishsum
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For bolt rifles it's common practice to back off the FL sizing die a bit so it will neck size without moving the shoulders back - but it does still resize the lower case body somewhat. In most cases I think that's just as good as a dedicated neck sizing die - at least from my experience.
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Old January 7, 2013, 08:38 AM   #4
Bart B.
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Using a full length sizing die on bottleneck cases such that it doesn't size all of the fired case neck results in setting the shoulder forward. That typically ends up making the case a bit hard to chamber; the bolt binds a bit when its closed on such cases as there's not enough room for that oversize case to fit in.

Accuracy degrades when the bolt closes hard. It doesn't seat in exactly the same place each time. Which is why, back when benchresters neck sized their cases, they had to full length size them once in a while as they grew enough to no longer chamber easy.

But most benchresters quit neck sizing some years ago. Proper full length sizing with the right die doesn't make the smallest groups shot any smaller, but it does reduce the size of the biggest ones. So, the overall accuracy's improved by using proper full length sizing dies set up correctly in the press. Note that full length sizing dies end up putting the sized neck better centered on the case shoulder than neck sizing dies do.

It's a popular belief that a chambered round rests in the bottom of the chamber. Another popular belief is that bottleneck cases headspacing on their shoulders neck sized fit the chamber better than full length sized ones when fired. 'Tain't so. Here's why.

All bottleneck cases headspacing on their shoulders center perfectly up front in the chamber when they're fired. The firing pin drives them there and as the case shoulder's the same size and shape as the chamber shoulder, it's easy to understand that the case will center perfectly in the chamber at the shoulder when fired. Bottleneck headspace gauges center in the shoulder when they're pressed there with a tight fit therefore so do loaded rounds. And in-line ejectors press the round into the chamber shoulder before the firing pin drives it there harder. So there's a bit of clearance all the way around the case body for most of its lenght to the chamber wall. And the back end of the case is pressed against the chamber wall opposite the spring loaded extractor anyway, so it's never centered anyway.

If one must neck size, get a die that does it correctly and does not touch the case body at all. To make a valid comparison, one needs to properly test their ammo made with each process to see the difference. Otherwise, any sizing tool and method may well end up doing the best when only a few shots are used to test each one.
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Last edited by Bart B.; January 7, 2013 at 10:06 AM.
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Old January 7, 2013, 10:19 AM   #5
603Country
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As usual, BartB is correct. But...I do believe (from years of doing it), that partial resizing will work just fine on some cartridge cases. It'll work on most if not all cases, but the ones with more taper work better. For instance, I get great results with my 220 Swift and my 270. I get poor results in partial resizing for my 223 and my 260. With the tapered cases, you don't bulge the shoulder out because the die doesn't touch the shoulders of the cases. With the cases that have less taper (223), the die does touch the shoulders when you partial resize and that causes the shoulder to be pushed forward a bit. You'll then have a 'force-fit' of the loaded round when you chamber it, and that degrades accuracy.

So yes, you can partial resize cases by use of the standard FL sizing die (directions per the internet, Nosler reloading book, or the Lyman reloading book). Nosler shows short simple directions how to do it. If you are a competition shooter, partial resizing probably isn't what you want to do, but it you are a hunter and paper puncher, it works just fine (with the right cases). But when you can feel the reloaded round being force fit to your chamber when you close the bolt, it's time to FL size those cases again.
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Old January 7, 2013, 10:40 AM   #6
MtnCreek
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I’ve had issues with some cartridges when trying to keep cartridge headspace in tight tolerances using a typical FL sizing die. Even with carefully sorted brass and consistent lubing, some cases will vary by a couple thou. I started using bushing dies on two cartridges I load for and that has eliminated the problems I was having. If you want to keep cart headspace consistently tight, consider going with a bushing type die. The typical neck dies (like rcbs) are a waste of money IMHO. I have several that I purchased years ago and never use them.
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Old January 7, 2013, 11:31 AM   #7
Bart B.
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603's right, partial sizing does work on some bottleneck cases. Those with a lot of shoulder taper are usually OK, but just be sure the die's body does not touch the case body else the case shoulder will start being pushed forward.

MtnCreek, the cause of a lot of case headspace spread using full length dies is typically a problem with the lube used. It's either too thick or unevenly applied to the cases. The amount of friction between the lubed case and die is enough to cause the press to spring upwards. If that spring's not the same amount, sized case headspace will happen. So the lubricity of all the cases has to be the same else their shoulder's gonna be at different distances from the head.

I had this problem using all the popular pad and finger rubbing techniques to put lube on cases. Suggested I use a thinner case lube; a 60-40 mix of STP engine oil treatement and Hoppe's No. 9 bore cleaner. So I did. Included with the suggestion was to tumble cleaned cases in a can with a foam lining that's had a few drops of this 60-40 mix dribbled around it then tumble 40 to 50 cases at a time as it turned on a Thumbler's Tumbler. This worked very well and sized case headspace got back to under a .002" spread. And the cases sized much easier than all the other standard lubes sold as case lube.

The other way to fix this is to use Redding's competition shell holders that come in height steps of .002" above the .125" standard. Use the one so when your die's bottom stops against it with the press's ram all the way up, the case will be sized the same each time.
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