Case Cocentricity

Discussion in 'Reloading' started by Dry Powder, Nov 30, 2008.

  1. Dry Powder

    Dry Powder Member

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    Hi gang I am new to the forum and have some technical questions on Rifle brass cocentricity. I just purchased a new Savage 12BVSS in 22-250 and 200 new WW Brass cases. I also have a new Redding Competition Bushing type die set. (Neck die, Body die and Seating die) I did the following to the unfired brass, Pocket uniform, Pocket de-bur inside, chamfer necks inside and out and sorted by weight. I did not turn the necks and would prefer not to. I did run them through the Neck sizing die with the appropriate bushing (.249) Neck OD less .003 as recommended by Redding. This operation just barely affected the necks if at all. I have neck runout of +/- .002 to .005. Here is my question: How can I get the brass closer in cocentricity? I would like to have no more than +/1 .001 or less if possible. I loaded 20 rounds very carefully and the bullet runout is not acceptable. I have ordered a Redding Full length die, will that get the cases lined up better. If I fire the cases will they become more concentric? Any comments would be greatly appreciated! gun)
     
  2. britz

    britz Well-Known Member

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    hey man, welcome!

    I also have a 12 fvl 22-250 and encounterd similar problems with winchester brass haveing lots of runout (all had .002-.004 and some as high as .007). I messed around quite a bit with it and it seems that after being fired the first time runout decreased. I also opted to turn the necks and now I have vertually no runout. I don't use a bushing sizing die however so I have very low neck tension. I plan on continuing with my turning for the 250 but not in the wsm's I load for. After the initial firing and partial fl resizing I have runout of .002 or less on a few cases.

    my personal theory is that the size of the shoulder compared to the size of the neck on the 22-250 makes it more suseptible to deformation due to the change in thickness of the neck on one side or another. Like I said, it's just my personal theory, doesn't mean it's true by any means lol!

    good luck,
    Mark.
     

  3. Dry Powder

    Dry Powder Member

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    Hi Mark,
    Thanks for your reply. I have been reloading for many years but recently decided to move up to the next level in reloading precision, man it's a whole new ball game. It is frustrating to buy such high-end dies etc. and know that I will not achieve the precision I wanted right off the bat. I believe that runout (Case and Bullet) is probably the biggest factor in poor groups. However I do think that these cases should improve with the first firing and then I should be able to produce some very precise cases and then hopefully very accurate rounds. I have had great luck in the past with standard dies in a number of calibers being able to achieve consistant minute of angle groups with hunting rifles so I hope to achieve some .5 or less groups with this Savage. I have a machinist back round and know that I should be able to achieve near perfect loads which should allow a good rifle to perform up to it's potential as long as I do my part. To me that is the challenge and joy in reloading!
    Thanks for your input.

    Nick
     
  4. britz

    britz Well-Known Member

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    I know what you mean about frustrating. When I first encountered my runout problems w/ the 250, I made a concentricity guage using an old dial calaper and some scrap wood and epoxy (pretty much jerry rigged but it works). Then I purchased a $99 redding comp seating die and was astonished to see runout yet. Then I turned necks and resized agian ---> still had runout! Next I fired the rounds and then resized them agian, No runout. So, I'm not certain if the turning really did it or if it was a combination of many factors.

    I have been finding that with my rifles (all factory rem, Tikka, Savage, winchester) one of the biggest factors that helped me gain accuracy was creating a crush fit when chambering the rounds. I am not able to seat to the lands on any of my rifles so I have to rely on the case itself to perfectly center bullet to bore. I have started PFL resizing and have good results so far. For my WSM's I have comp shell holder set which is nice, but for my 250 I am simply backing the die off a little. I would like to simply neck size but I find that after a couple loads both my 22-250 and my 300 wsm get really sticky bolts and the groups go the heck at that point too. So, I have been simply PFL sizing all the time. Probably a little harder on the cases, but I want accuracy and reliability --kinda obsessed with it lol!
     
  5. boomtube

    boomtube Well-Known Member

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    Sadly, it seems from reading on the net, that problem is sorta common with those bushing dies.

    I prefer the Lee Collet Neck sizers. They work necks the absolute minimum so case life is good. They need no lube, make straight necks and the neck ID is always right no matter the neck thickness. And no seater can make straight ammo if the necks are bent!

    Understand that no sizer die can make non-concentric necks absolutely straight. Depending on your brass, you may need to lightly turn your necks, just a skim cut, to remove the worst of the high spots before you see much improvement.

    And yes, shooting WILL make the necks pretty straight IF your chamber is straight. Thankfully, it seems most are but not always.

    Try a light turning, Lee neck size, shoot and then Lee neck size again. At that point your case run-out should be quite low.

    You didn't say how you are reading the neck run-out now. Remember that true run-out, or tilt, is half of the total indicated run-out.
     
    Last edited: Nov 30, 2008
  6. Dry Powder

    Dry Powder Member

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    Hi Mark
    Thanks again for another good reply. I am glad to hear that your process finally worked. After I try a full length sizing if I don't get straighter cases I will go ahead and turn the neck. At this point the neck walls do check very consistant in wall thickness. Following that I will of course Fire the cases and go from there. In the past I did use PFL sizing and got good results. In this case with my new Redding Comp die set I will try to neck size about 3/4 of the neck and then use the body die when needed to get that very slight crush fit I expect that is where I should attain my best accuracy. My goal though is to build some acceptable loads for a PDog hunt this coming year with new brass and that will require a thousand cases at a minimum. The cost savings would be substantial if I can do it with new cases. In addition to the hunting loads I will try to make some real accurate target loads with fired cases. For those I will try to do the "Full Monte" and use all of the methods I can.
    Nick
     
  7. Dry Powder

    Dry Powder Member

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    Hi Boomtube,
    Thanks for the reply. I sure hear alot of good things about the Lee Collet Neck Sizer. I don't have one yet but it is starting to look like I am gonna need one. Let me ask you this: Would the Lee Collet Sizer improve the run out on new cases? Would the Lee do better than using the Redding FL die for this straightening process? I know this is just a "one time" deal for me with so many new cases to process. I am sure after the cases are fire-formed the Redding dies will do a good job in making concentric cases.
    I have an RCBS Case measuring gauge with dial indicator to do my measurments.
    Thanks for taking the time to answer my questions!
    Nick
     
  8. boomtube

    boomtube Well-Known Member

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    Dry, I don't think ANYTHING in reloading is a predictable fact. It's all cut and try. If it works, great, if it doesn't it may work next time! Who knows.... And I make no claim to be a expert, been at it over 40 years and still learning.

    That said, no die used today will make the cases work better in another die tomorrow so, no, even if the Lee should do you better with your new brass it will have to be used next time too.

    I suspect the "problem" with bushing dies is that the necks enter the bushing while the body of the case is still not touching the die walls. That means that any soft or thin spots in the neck will give way more and the neck will drift to that side. I think. Most of the time anyway.

    Lee's Collet die is unique. It has a bullet sized mandrel which also serves as the decapping rod. The mandrel is pretty well centered in the die body so the necks get a good chance of being squeezed down and kept straight. IF the necks are concentric, so the inner and out diameters are also concentric.

    I won't con you, nothing in this life is perfect including Lee's Collet neck die. It has a learning curve so those who are not willing to take the time and effort to learn to use it will be better served with some other type die. Other dies are pretty much a conventional "shove it in and pull it out" design while the Lee requires a developed feel to be consistant with the inside diameter. And, SADLY, some of them have internal rough places that may need to be polished smooth with a split dowel and sandpaper spun in an electric drill. Still, personally, the advantages of the collet neck dies out weight the disadvantages, by a lot, and at much less fuss and expense.

    I have no personal experience with anyone's bushing dies. Just know what I read on the web about them producing bent necks, as your's does. I KNOW the only way to get consistant bullet tension, as most people figure it, demands that the necks be turned to a constant thickness. Seems ALL of the magazine "experts" love bushing dies but I sometimes wonder about some of them too....

    Good luck!
     
  9. Clark

    Clark Well-Known Member

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    The brass gets concentric when fire formed.

    It can stay concentric when sized.

    If it is not concentric, sizing will not make it straight. When the neck of the case goes in the neck of the die, nothing is holding the body of the case.

    If you buy a concentricity gauge, you will see that the errors are:

    .004" from pulling an expander ball through the single step sized neck.
    .001" sizing with a bushing die with a chamber .006" larger than the loaded neck.
    .001" seating a bullet into an unsupported case.

    Non concentric ammo can only open groups from ~ 2" to ~ 4" larger at 100 yards with ~.004" eccentric ammo.
    If the ammo gets any worse, the chamber will bend it straight.

    Don't buy a concentricity gauge. They come with a little fortune cookie message that says, "You will probably find the expander ball is causing the problem."
    Just remove the expander ball, and save some money.
     
  10. Dry Powder

    Dry Powder Member

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    Thanks Clark.
    It seems that the expander is the root of most case prep problems perhaps even at the point of manufacture. I will be sure to avoid them as much as possible. I think I will try turning the necks on the new cases and see if that helps. Next I will fire-form what I have loaded and see what I have and then go from there. You guys are all great for responding! I will post my results as I go along.
    Nick
     
  11. boomtube

    boomtube Well-Known Member

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    "I will be sure to avoid them (expander balls) as much as possible."

    Welll ... with respect, my experience with and without expanders differs from Clark's. They call them things expander balls because they expand. Sizers, conventional sizers anyway, size case necks down too far and the expanders bring them back up to very near bullet diameter before we seat bullets. If we don't expand those too small necks with an expander of some kind we will have to do it with the bullet itself and that really ain't very good.

    First, it's very hard to get any flat based bullet to enter a too small mouth cleanly so the bullet heel tends to get damaged in the effort. Damaged heels are really bad for accuracy.

    Next, if you recognise that a standard expander ball is unsupported and pulls the necks out of line, figure out what using a loosely supported bullet as an expander is going to do to the necks as it gets pushed into an undersized hole.

    Finally, case brass is sorta thick, hard and tuff. Many bullet jackets are not so thick, hard or tuff. Using a relitively soft bullet, even jacketed, to expand a hard neck just doesn't seem good, at least not to me. To much chance to deform the bullet, at least a little bit.

    Get a Lee Collet neck sizer, or a Lyman "M" expander to use with your present size die, and be done with it.
     
    Last edited: Dec 1, 2008
  12. Clark

    Clark Well-Known Member

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    The brass comes concentric when new.

    The expander ball does .004" of bending if used in the same step as when the brass is sized, but much less if the brass is already sized.
    The expander ball can be used later to bell the mouth of the case for cast bullets with little effect on concentricity.

    That is, if the expander ball is removed, the brass sized, the expander ball replaced, the case inserted into the die only far enough for the neck to be expanded but not sized, then the ball is not pulling when expanding, but pushing.

    The reason for the big difference between pushing and pulling with the expander ball is that pushing against a shell holder is more balanced than pulling. If the shell holder is open on one side, that side hangs back in pulling and the neck is bent toward that side.

    In forming 6mmPPC brass from 220Russian, a mandrel is used and never an expander. I did not under stand the difference and wrote professor Bradshaw [assistant professor back in 1994]
    Load development in a benchrest rifle - rec.guns | Google Groups

    The answer was pushing vs pulling.


    Here is Bart Bobbit telling me how he made his own concentricity gauge:
    Setting up a concentricity checker. - rec.guns | Google Groups
     
  13. Buffalobob

    Buffalobob Writers Guild

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    I will add a couple of points

    A fired case is only as concentric as the chamber of the rifle. There are plenty of rifles with poorly cut chambers and out of alignment chambers ( I have two of them). There are also plenty of rifles with chambers that are close to Max SAMMI so the cartridge is rolling around in there laying on the bottom of the chamber.

    If you want concentric ammo you need a gauge otherwise you do not know whether you do or do not have good ammo. And you do not know why.

    Finally, putting good ammo in a bad chamber will help but it does not cure a bad chamber. That is why there are a lot of custom rifles used on this forum where accuracy is a requirement. You just got to have a good chamber.
     
  14. J E Custom

    J E Custom Well-Known Member

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    I have minimized this problem by outside neck turning.

    I know you said you did not want to do that but I found that preping the
    cases and doing a minimum outside turn on the necks made all the difference
    when fired the first time.

    The dies or the expander cannot true up the thickness varriations in the necks
    so I turn them before the first firing and let the chamber true the case up.

    After using this process the neck runout is as true as the chamber. Also if you
    outside turn before firing you can check the chamber Cocentricity before resizing
    the brass.

    I only turn enough to clean up the necks the same. all brass will have some
    differances in neck thickness so I true it up befor I start loading.

    Just the way I do it and it works for me.
    J E CUSTOM