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New brass - full resize or neck only?

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sakomato View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sakomato Quote  Post ReplyReply Direct Link To This Post Posted: February/24/2009 at 20:15
Originally posted by Sgt. D Sgt. D wrote:

 
 
I find this alarming! If a fired case is out of round, doesn't that suggest that the chamber is causing it? I had always expected that a fired round would to some point become custom fit to the chamber. I was thinking that the sizing die was primarily for correcting neck deformation and brass nearing the end of its usefulness. If the chamber is a presicion bore how can this happen?
 
 
Hey Sgt D, the fired case will not be out of round or have runout (chambers are almost always concentric or close to it).  When you fire the case the brass will iron itself to the chamber walls and will be very concentric on the outside.  Any variances in neck thickness will migrate to the inside of the neck.  Where it becomes out of round with runout is when you start resizing it.
 
Like Dave Wilson said, the expander ball is usually the culprit and it will jerk the shoulder and neck around.  If you size with the expander then that will size the inside of the neck brass and push variances in neck thickness back to the outside of the neck which will show up as runout but is really not.  If you size without the expander in a FL die then you would need to neck turn so as not to get too heavy a bullet grip but that would reduce runout since most dies are also very concentric.
 
If you use a Lee Collet then you will have less runout because the Lee Collet has a floating mandrel which will center before the collet is squeezed onto the neck.
 
With a bushing type neck sizer most of us remove the expander ball because you might as well be using a FL die if you use a bushing die with an expander.  Without the expander you can buy a bushing to fit the size you want on the outside of the neck.  But again, you need to turn to get the best results because the bushing will size the outside of the neck and push all the neck thickness variations to the inside, that will lead to good runout on the case neck before seating the bullet, but bad runout after seating the bullet since the bullet will push the inconsistencies back to the outside and push the bullet one way or the other.
 
Lot to think about.  Best course is to use a Lee Collet Neck Sizer and Redding Body Die and you have solved 95% of runout problems without a lot of hassle.


Edited by sakomato - February/24/2009 at 20:16
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: February/25/2009 at 09:44
Originally posted by sakomato sakomato wrote:

 
Hey Sgt D, the fired case will not be out of round or have runout (chambers are almost always concentric or close to it).  When you fire the case the brass will iron itself to the chamber walls and will be very concentric on the outside.  Any variances in neck thickness will migrate to the inside of the neck.  Where it becomes out of round with runout is when you start resizing it.


Hope I can explain what I saw on the vid with this.

David tubbs said that based on the brass that the entire case can in fact become unstraight in a chamber upon firing and will stay that way. 
He said what causes this is if the case walls are not even from side to side or at lease very close that the thinner side will stretch and it will bend like a banana. (obciously not that much but that was just the example that he used)  He said it is more likely in a action like a Rem 700 because there are only the two locking lugs for it to push against when firing.  If you put the thin side so it is not pushing on the lug but so it is in position in front of nothing that the brass will actually stretch that way.  That is one reason why a lot of bench rest shooters put their brass in the exact same way every time, so they can line up the weak and strong side perfectly with the lugs on the bolt. 

He use a guage to measure the case walls of his brass and throws out anything that was over .003 variance from side to side.  He said using an action with more than two locking lugs definitely helps this problem.  But for extreme accuracy and consistancy we just need to be checking the case all thickness often and throw out the brass that is much out of spec. 

Obviously this is for the most extreme accuracy obtainable and will not apply to most of us, just thought it was some very interesting info.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cheaptrick Quote  Post ReplyReply Direct Link To This Post Posted: March/02/2009 at 08:59
Originally posted by Roy Finn Roy Finn wrote:

On brand new virgin brass, I fully resize on the first loading and for my rifles, I neck size from then on. Not sure why your brother in law is only getting two cycles on brass. Depending on the chambering and how hot you are loading, trimming shouldn't be necessary all that often. What I do on new brass, is to trim back about 5 thousands. Trimming also squares up the neck on virgin brass and once that is done you are good to go.
 
What Roy said.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sgt. D Quote  Post ReplyReply Direct Link To This Post Posted: March/02/2009 at 12:18
So when I am sizing the neck on new brass or pushing primers and sizing fired brass the resistance I am getting on the return stroke is "possibly" causing runout. Or maybe even pulling the neck and shoulder out of place. This is getting frustrating. I had wondered why the pull stroke was smooth and had almost no resistance, but the return is usually tight at the end. Is there an adjustment to reduce this or do I need different dies? I am using RCBS now.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: March/02/2009 at 12:35
David Tubb recommends taking the expander ball that goes inside the case and sanding it down a little smaller.  That is what he did in the video.  He says they are to big to start with and will pull to much and cause run out.  He chucked the whole expander ball assembly in a drill and used sand paper and emery cloth to make it smaller.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cheaptrick Quote  Post ReplyReply Direct Link To This Post Posted: March/02/2009 at 12:42
Or, you could throw the factory expander ball in the trash like I did and use a K&M Case Neck Expander, if and when necessary.  
 
I believe that the expander button, along with the case trimmer pilots, are the 2 biggest culprits causing run out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steelbenz Quote  Post ReplyReply Direct Link To This Post Posted: March/02/2009 at 14:10
Originally posted by cheaptrick cheaptrick wrote:

Or, you could throw the factory expander ball in the trash like I did and use a K&M Case Neck Expander, if and when necessary.  
 
I believe that the expander button, along with the case trimmer pilots, are the 2 biggest culprits causing run out.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sgt. D Quote  Post ReplyReply Direct Link To This Post Posted: March/02/2009 at 20:18
Originally posted by cheaptrick cheaptrick wrote:

Or, you could throw the factory expander ball in the trash like I did and use a K&M Case Neck Expander, if and when necessary.  
 
I believe that the expander button, along with the case trimmer pilots, are the 2 biggest culprits causing run out.
 
Ok if I trash the expander ball, what will determine the need for a expander? Do I have to mic each case or is it easy to see? I don't mind an extra step of two as long as it doesn't cause problems somewhere else.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sakomato Quote  Post ReplyReply Direct Link To This Post Posted: March/02/2009 at 20:54
Hey cheaptrick
 
What size does the K & M expander size the inside of the neck to?  How much bullet grip does it give?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 300S&W Quote  Post ReplyReply Direct Link To This Post Posted: March/03/2009 at 07:17
 I use a universal depriming die and Lyman "M" dies instead of the expander/depriming rod assembly.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cheaptrick Quote  Post ReplyReply Direct Link To This Post Posted: March/05/2009 at 14:59
Originally posted by sakomato sakomato wrote:

Hey cheaptrick
 
What size does the K & M expander size the inside of the neck to?  How much bullet grip does it give?
 
I have one for a .308, so it expands the case mouth to .308. 
Neck tension obviously is very minute on most quality bullets.
If that's the case I just run them through my Lee Collet die to get a few thousands neck tension .    
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sakomato Quote  Post ReplyReply Direct Link To This Post Posted: March/05/2009 at 22:47
So you would have to have another die to size the neck after the K & M expander.  If you have the Lee Collet then why do you need the K & M expander?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cheaptrick Quote  Post ReplyReply Direct Link To This Post Posted: March/06/2009 at 05:34
Originally posted by sakomato sakomato wrote:

So you would have to have another die to size the neck after the K & M expander.  If you have the Lee Collet then why do you need the K & M expander?
 
I only use the K&M expander to open the case mouth on virgin brass to turn necks or just open the case mouth if it gets pinched. 
The K&M expander only sizes the inside of the brass, not the outside.
 
I have used the K&M tool on several occasions to expand the necks and the bullet seated OK, with little bullet "grip". But some rounds are too loose and will slide up and down.
So to get consistent neck tension, I run all the brass again through my Lee Collet die.  
 
Actually, once the brass is fired, you will only have to size the outside of the brass any how, thus eliminating the need for the dies expander button.
 
I apologize for not explaining myself better. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BillyWayne Quote  Post ReplyReply Direct Link To This Post Posted: March/06/2009 at 10:45
I cannot get new brass into my Lee Collet dies.  The necks are to tight.  But once they have been blown out the Lee Collet works great.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Stick Quote  Post ReplyReply Direct Link To This Post Posted: March/08/2009 at 18:41
Never move brass,without a reason.
 
Neck sizing virgin hulls will round necks,align neck tension and preclude inducing headspace woe. Easy to back an FL die off,to accomplish sizing the greatest portion of the neck,less influx of setting a shoulder back.
 
Die/chamber geometry is the most misunderstood and most botched facet of Reloading.................
 
 
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