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Full length sizing VS neck sizing

 
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Old 02-20-2010, 09:49 AM
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Full length sizing VS neck sizing

I am just wondering if it makes a difference weather i full lengh size or just neck size my brass. Does it make the brass get more shots? Does it affect accuracy? Is there a reason that i should go ahead and buy the neck sizing die instead of full lenght sizing all of my reloads? Thanks for any answers you can give me.
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Old 02-20-2010, 10:15 AM
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Re: Full length sizing VS neck sizing

How long your brass lasts will depend upon how far you push the shoulder back when Full Length Resizing. When you push the shoulder back farther than ~.002" or so then the brass has to re-expand everytime and it will lead to thinning at the pressure ring and reduce the life of that piece of brass. If you push the shoulder back to new case dimensions everytime, you will soon have a case head separation and will lose that piece of brass, or worse yet damage the gun or yourself.

Neck sizing is good for the life of the brass but not good for hunting loads that may be too tight to chamber without too much resistance in the field. Also, because of inconsistancies in chambers and fire formed case bodies, neck sizing has not always given me the best accuracy.

IMO, accuracy is best when Partial Full Length Resizing where you size the neck, case body and only push the shoulder back ~.001" or so. You will also get good brass life.

YMMV
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Old 02-20-2010, 03:18 PM
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Re: Full length sizing VS neck sizing

Even if most of your ammo is neck sized you still need a full length sizer.
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Old 02-20-2010, 04:08 PM
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Re: Full length sizing VS neck sizing

Quote:
Originally Posted by boomtube View Post
Even if most of your ammo is neck sized you still need a full length sizer.

that is the one thing i did know
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Old 02-20-2010, 06:50 PM
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Re: Full length sizing VS neck sizing

On BR central, they did a survey several months back with well over 50% of the BR shooters saying that they FL size. Most guys NS only are throwing the brass away after 3-4 firings and starting over. Most use carefully selected dies to minimally size the body while giving the shoulder bump.

Minimal sizing is key to long brass life and it looks like for best accuracy too.

No way to NS only long term, as brass will expand to eventually not chamber. Got to FL size or at least use a body bump die to resize the case body or throw it away.

IMO there is no such thing as partial FL sizing IF a die is cut for that chamber. Kind of like being partially pregnant.

If you are sizing to at least touch the shoulders you are getting the full sizing on the body. So what are you partially sizing? Maybe the better term is minimal shoulder bump.

BH
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Old 02-20-2010, 09:04 PM
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Re: Full length sizing VS neck sizing

The Neck size vs FL size argument has benn around since before I started reloading in 1965. Does it help case life? That depends. If your chamber has a large dia. neck and that case necks are what splits first on your cases no. If your case body is oversized and you are working it alot each time you size yes, definately neck size. Does it help accuracy? In some rifles with some loads. Bumping back the shoulder. That is something that really veries. I have had rifle that I never bumped back the shoulder with brass I had fired 20 times before the case mouth would split. The hotter you load the greater the need to bump back the shoulder. I also have meet afew guy that shoot bechrest compation that do not size at all. They turn their case neck to zero expantion and simply knock out the old primer, put in a new one, dump in the powder and seat the bullet. Personally I like .002 of neck expantion because almost all of my shooting is in the field and I like to have a small margin for error, or should I say dirt.
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Old 02-21-2010, 08:07 AM
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Re: Full length sizing VS neck sizing

The most accurate rifle's I know of are that way because they shoot reloads with properly full length sized cases in standard SAAMI dimension chambers. If one doesn't use the right tools and techniques, their experience with full length sizing will convince them its the Devil's doing disasters with your reloads as far as accuracy's concerned. Here's the details on how to full length size rimless bottleneck cases a proper way.

But first, note that a rimless bottleneck case fits the chamber when loaded and fired. When chambered, it's back end is pressed sideways by the extractor so it bears against the chamber wall at its pressure ring. If the bolt's got an inline spring loaded ejector, that pushes the round forward until its shoulder stops and centers in the chamber shoulder. If the case neck's well centered on the case shoulder, it will be centered in the chamber neck. It doesn't matter how much clearance there is around the case neck. As there's no such thing as a perfectly round chamber or case, if the case is oriented in the chamber such that its major radius at its shoulder is at the minor radius of the chamber shoulder, there may be enough interference to make the front of the case align off center at its neck axis.

Full length sizing dies should reduce case body diameters no more than a couple thousandths; enough to prevent any case body contact/interference with the chamber wall between pressure ring and shoulder. Any more and case life gets less and less. More important for accuracy, the fired case shoulder needs be set back no more than 2 thousandths. Any more shoulder set back lets the back end of the case stretch more after the firing pin smacks the primer driving the case hard into the chamber shoulder setting the case shoulder back a few thousandths before the round fires. When pressue builds pressing the front half of the case body against the chamber and the back half of the case stretches back until the case head stops against the bolt face, the more that back half has to stretch means quicker thinning of the brass at the pressure ring.

Full length sizing as above, I've got as many as 47 reloads on a .308 Win. case fired in a standard SAAMI chamber with a .345" chamber neck diameter and loaded round neck diameter of .337; that's 4 thousandths clearance around the case neck to chamber neck. Others have got a lot more. And all with normal, safe maximum loads.

High power match rifle competitors used to lap the necks out on their standard full length sizing dies to about 2 thousandths smaller than a loaded round's neck diameters. Nowadays, both Redding and RCBS make full length busing dies that do the same thing. As long as your chamber's at standard (minimum) SAAMI specs, one of these dies should work well. Otherwise, Alan Warner can make you a full length die for your particular chamber that'll work:
Warner Tool Company - Reloading Dies
Other custom die makers can do the same.

Full length sizing fired cases typically centers the neck on the case shoulder better than neck sizing dies do; the case body's fully supported as the neck's swaged back down. And setting the fired case shoulder back keeps the case from binding when the bolt's closed. Neck and partial neck sizing of fired cases typically lets the case bind a bit when the bolt's closed; especially partial neck sizing with a standard full length sizing die that usually moves the fired case shoulder forward a bit causing the bolt to close harder than when the chamber's empty.

When the bolt binds, it doesn't seat at the same place for each shot. Accuracy suffers when this happens. But accuracy from fired cases partial neck sized may well be better than when a full length sizing die sets the case shoulder back too far.

Since the 1950's, Sierra Bullets has been full length sizing all their cases used to test their bullets. Their test barrels have standard SAAMI dimension chambers. They used to use neck lapped standard full length sizing dies but now use Redding Full Bushing dies for cartridges these dies are made for. All other cartridges Sierra reloads are sized with standard Redding full length sizing dies. I doubt anyone shoots their bullets as accurate as they do.

Last edited by Bart B; 02-21-2010 at 08:13 AM.
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