Help me determine what is causing my runout!

Discussion in 'Reloading' started by dmproske, Aug 15, 2009.

  1. dmproske

    dmproske Well-Known Member

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    Am loading once fired brass (batch of 50 Winchester) out of a Remington M700 in .308 Winchester.

    Measuring runout with a Sinclair runout gauge.

    Runout started at half a thousandth to 1.5 thousandths right out of the chamber. Sized them with a Lee Collet die. Most ran 1 thousandths to 3 thousandths neck runout. There were a few that ran more than that, but I culled them out. All were inside chamfered.

    I seated 168 SMK's using a Redding competition seating die. A few had really good bullet runout 2-3 thousandths, but the norm was 3-5 thousandths. Some ran really high....like 8-10 thousandths. A couple was like 12-15, but I pulled the bullet, resized the case and reseated, and was left with 7 thousandths for that one....

    How in the world can a case that starts with 1-2 thousandths neck runout, end up with 5-8 and sometimes greater bullet runout when seated with a precision die like the Redding Competition seater???

    Is it varying inside neck thickness? I understood that was pushed to the outside when sized with the collet die, and would show up in neck runout?

    Is better brass like Lapua the answer? I could neck turn, but I have a factory rifle, and understood that neck turning could have negative effects in a loose chamber.

    Thanks in advance
     
  2. kraky2

    kraky2 Well-Known Member

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    Does Redding have any choices for the seating stem (the cup that pushes against the tip of the bullet). If so I have found on some dies that getting a stem that fits the profile of the tip of the bullet can make a big difference.
    Hornady makes stems that fit their A-max line of bullets and they work really really well with plastic tipped and vld type bullets.
     

  3. Winchester 69

    Winchester 69 Well-Known Member

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    Have you tried loading with your dies on a friend's press?
     
  4. esshup

    esshup Well-Known Member

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    I seat the bullet 1/3 of the way, rotate the case a ways, seat another 1/3, rotate again and final seat.

    When I was having problems with runout, after much help from the guys here and a LOT of searching, I found that my shell holder was crooked. A new shell holder fixed the problem. I never knew I had a problem until I started checking runout. Sometimes the gun would shoot really good groups, and other times not so good. I thought it was a problem with the gun, but it turned out to be a problem with the loading process.
     
  5. AJ Peacock

    AJ Peacock Well-Known Member

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    There are a number of things that can cause runout. The first, you've discovered is the neck thickness. This is pretty well taken care of by using the Lee collet die.

    I'll list a few things that are easy to check and fix, each of these items are things I have found can lead to larger runout. These aren't my ideas, I've just 'collected' them over the years.

    1) Float your shell holder. If you still have the spring clip that holds your shell holder in place, get rid of it. Either use your press without anything holding your shellholder in place, or put a small rubber band or O-ring around the slot to hold it in place. I don't use anything to hold the shellholder in place. This change will allow your shellholder to self center as the cartridge goes up into the die.

    2) Be gentle. When you are resizing and when you are seating your bullet, be gentle with your stroke. I don't do the stroke all at once, I let off the pressure as the cartridge starts into the die, so the shell holder can center itself. Also, I use nice even pressure as I seat the bullet.

    3) Chamfer your brass, this lets the bullet start into the brass with less initial force. The larger force can push the neck and cause neck runout.

    4) Lightly clean/polish the inside of your necks with a brush wrapped in steel wool. I put an undersized cleaning brush in my drill press, wrap it with a little bit of 0000 steel wool and lightly polish/clean the inside of my brass necks. I run the drill press on it's slowest speed. This gives me more consistent neck pressure and more consistent feel while seating bullets.

    5) Make sure the seating stem on your seating die is touching the bullet all the way around and not bottoming out on the tip of the bullet. You'll probably need to take your seating die apart to check this.

    6) I used to seat the bullet in 1/3's and then spin it a bit and seat the next 1/3 of the way, then spin it and seat it the rest of the way. I don't do this any more with my good seating dies. With my old standard seaters (cheapy RCBS stuff), I still do this.


    Those are the simple ones. I'd highly recommend the book by Zediker about reloading for competition. Zediker Publishing

    AJ
     
  6. boomtube

    boomtube Well-Known Member

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    "what is causing my runout!"

    Well, it's really hard to be sure from here but we can try.

    First, I wonder how long you have used the gage, and how you are using it and how you are intrepreting it.

    Taking the last first, maybe I can cut your runtout in half immediately. I can't imagine any case sent through a Reddiing (or Forster) seater can exit with .015" of real run out (RO). You do understand that what you see on the gage is called Total Indicated Runout (TIR) and that the actual RO is only half of TIR?

    No seater can correct for a bent neck. With the Sinclair tool, I think neck RO is taken near the mouth while the body supported at the base and just below the shoulder, right? So, RO mostly shows how much out of alignment the neck is to the centerline of the body. Very little of that RO comes from the seater, per se, so hopeful efforts to correct by seating part way, turning and completing seating isn't really going to do much good.

    Consider that if a neck were 1 1/2" long and you took one reading at the present location, then a second near the outer end, the second reading would be much greater simply because the angle of error shows more difference the further away from the start of the error it's read. The anglular error would be unchanged but the TIR would appear greater. Meaning, if we carefully push a bullet perfectly straight nto a slightly bent neck, the dial indicater will swing further when we measure off the tip simply because it's reading further out. If that's what you are seeing, understand that the "real runout" remains only that of the bent neck AND only half of the TIR, and it's due to the bent neck, not so much the seater.

    Most sizing dies and chambers are perfectly straight, or nearly so. But, pulling a largely unsupported expander out of a totally unsupported case neck almost guarantees the necks will be pulled out of perfect alignment, each time we size/expand them. All factory case necks have thicker:thinner sides. The thinner side will give way, stretching more than the thicker so the neck CL will tend to drift as the expander is withdrawn.

    Obviously any angular difference between the between the center lines of the inside diameter (ID) and outside diameter (OD) of a pipe/neck can't be corrected with a die. Nor is alignment likely to be correctable with a reamer. Reamers make the necks thinner but they tend to follow the existing hole while doing it.

    Concentricity out of the seating die requries that the inside, not the outside, of the neck be concentric and no conventional die can assure that. Correcting that requres outside neck turning as the best way to improve the neck ID and OD centerlines.

    That starts with obtainly the best possible necks before turning.
    Obtaining a sized but still straight neck is best done with a Lee Collet Neck sizer die. I've also found the Lyman "M" die expander used with a stripped FL die to be a close second. That's because the M expander it pushes IN, instead of pulling OUT as conventional ball expander does. Neither is die is magic, they can't fully correct for all of the neck's error but using either is MUCH better than a conventional sizer/expander.

    When the inside of the necks are as straight as you can make them, turn the outside to (try) to make the outsides match the innerds. Turning neck for factory chambers has limited value, don't bother skinning off more than perhaps 70-80% of the circumference. The Forster Hand Operated Turner (HOT 100) is the least expensive, easy to use neck turner with a carbide cutter and micrometer type adjustment knob I know of. It's NOT "BR" grade but it is plenty good for factory chambers; try it.

    Conclusion; Concentricity requires good necks, good necks requires fairly good brass that's very well selected and prepped. All any good seater can add is to not destroy what the case prepping has done.

    Good luck!
     
  7. Mikecr

    Mikecr Well-Known Member

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    I don't agree with generalizing TIR-vs-R(cutting TIR in half) because your runout cause would first have to be determind before going there. For example, if your runout is caused by big variance in thickness, this will be indicated regardless of centerline conditions. And in this case, your runout would be exactly as indicated(provided that is your only contributer).
    Also it would be pretty rare that a positive variance will be followed by an exactly opposite negative variance with brass, because that would mean only one specific contributer, with no others combining in the abstract. That's not reality in my experience.

    I also do not follow the collet die as a runout reducer idea. I just don't see how it would. What I see, is that it would contribute less towards additional runout. And as you have seen for yourself, it did not reduce runout.

    You did not mention which Sinclair runout gauge you're using. I hope it's a standard V-block/bearing type. If not all bets are off.
    If it is, then I would be very concerned about that initial runout measured right out of the chamber(before sizing). There should be essentially zero TIR on the necks at this time. If not, you've got an ugly chamber flaw(unlikely), or very high thickness variance in your brass, -producing bananas.
    Don't assume any particular brand of brass is better in this regard. It varies from lot to lot in all of them.
     
  8. AJ Peacock

    AJ Peacock Well-Known Member

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    Unless I'm misunderstanding you, I'm confused. If you load a bullet .001" off the centerline of the cartridge case, you will measure .002" TIR. How could TIR and R not be related in a 2-1 relationship?

    Unless you are talking about a neck that is crooked, then you should get vastly different TIR close to the neck and closer to the point.

    AJ
     
  9. boomtube

    boomtube Well-Known Member

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    "..if your runout is caused by big variance in thickness, this will be indicated regardless of centerline conditions. And in this case, your runout would be exactly as indicated(provided that is your only contributer)."

    If I correctly interprete your meaning, you are suggesting a potential for the neck ID to be exactly paralllel to the OD but off-set by what ever neck thickness variation that exists?

    IF I do understand you correctly - and I may not - I don't agree with your perceived view of gaged TIR vs. actual run-out. The high side will read one level of error away from the true center line. A reading on the other side will read the same off-set but in the opposite direction. So, no matter the source of error, the indicated reading will effectively be twice the amount of actual run-out. That's just the way TIR works, regardless of the source cause of the error. (And a tip of the hat to AJ)

    I'm told that many non-machinest's have some difficulty grasping the difference between run-out and TIR and how either is measured. (I'm NOT a machinist but I've had a good deal of hands-on lathe training from someone who is.)


    "I also do not follow the collet die as a runout reducer idea. I just don't see how it would. What I see, is that it would contribute less towards additional runout."

    Again, if I understand, it's hard to differentuate between not adding runout vs. correcting it. To some slight degree, the Lee collet die does both.

    First, unlike a conventional small sizer button dragged through the neck, the Lee collet die cannot ADD any "bend" to a neck since the neck is squeezed hard against the straight, centerally mounted and firmly held mandrel. That's good, and it's unique to that die.

    Second, if the inner case neck was originally formed with some anglular difference to the outside, the fact that the inside is forced so hard to the mandrel there will be some amount of straightening force applied. Including springback, there are too many variables in that for anyone to project just how much such a straightening would remain after the sizing pressure is removed but it sure can't get worse and it MAY be improved.
     
    Last edited: Aug 15, 2009
  10. Mikecr

    Mikecr Well-Known Member

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    All I'm saying is the runout may not be bent necks. Or necks off center. It could be both.. Or the case bodies can form into bananas(because of springback variance, due to thickness variance), throwing everything out.
    There could be a combination of these things among others adding and subtracting in ways that don't just go up and down.
    This isn't lathe turned stock, it's pressure formed.

    For example, an angle might counteract an offset, or add to it. Let's say one or the other is significant. Until it's specifically measured, you couldn't really generalize about it. You can't just divide runout in half, because you could actually have more than that, it's just being counteracted by the other contributor.
    You don't run into this often in machining, because only one parameter is being changed at a time. Step by step by step.
    And identifying runout is similar in that you go backwards through the steps.

    Now you could have a die issue, shellholder, or more common press alignment issues. The seater plug might be a contributor.. Good things to checkout.
    But the base of all runout, even with all else perfect, is case thickness variance. It runs full length of the case. With this, runout will occur and grow with each firing, and with each contact with any die.
    The devil here is springback, and if your not considering what's happening in that regard you might convince yourself of a die issue that isn't. The die is just releasing an inconsistent tension, and there is nothing I know of that can fix it. There are only things done to reduce the rate of runout growth(like neck turning & minimal sizing).

    The fella starting this discussion mentioned runout before dies even touched the brass. This is significant in that it's independent of what has been discussed so far, unless he FL sized before fire-forming. I think he should go back to that. Fix that first.
     
  11. dmproske

    dmproske Well-Known Member

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    Yes the runout numbers I posted were what I was reading on the gauge. So TIR would be half that. Runout on cases right out of the chamber was almost nothing as would be expected.

    I am using the standard Sinclair gauge, the roller bearing type.

    Yes the cases were inside neck chamfered.

    Yes I am the spring clip to hold the shell holder on the press. I will take it off next time and see if the numbers improve.

    I am seating Sierra Match Kings. I would expect the .308 Redding Comp seating die stem to accomadate those quite well. I will take the die apart to see if there is debris in it or something else ammis.

    I am the only person that I know that reloads so I cant try these on another press.

    I always rotate the case and seat in several steps, always go easy on the handle to let things line up.

    I am using a Lee Classic cast single stage. Is there a way for the average joe to measure press alignment issues?
     
  12. AJ Peacock

    AJ Peacock Well-Known Member

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    Press alignment is tough to measure and is unlikely to be the cause. A shade tree mechanic method of seeing if the threads on the top are straight with the ram is as follows.

    Put a die in the press and raise the ram, screw the die in and see if the bottom is square to the shellholder, if you screw it in just enough to let a very small gap, you'll be able to tell if its pretty square. Some of the cheap loack nuts will not lock the die in as square as others, so be aware of that as you lock the die in.

    AJ
     
  13. CliffM

    CliffM Well-Known Member

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    In addition to all the other things try removing the spring from the inside of the die. I've found that the spring pressure can sometimes start the bullet before the case has risen high enough to be aligned by the die. Cliff
     
  14. boomtube

    boomtube Well-Known Member

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    "... base of all runout, even with all else perfect, is case thickness variance. It runs full length of the case. With this, runout will occur and grow with each firing, and with each contact with any die.
    The devil here is springback, and if your not considering what's happening in that regard you might convince yourself of a die issue that isn't."


    Okay, I see your point. Disagree with how it can be measured but your point of bad brass is well taken. I do sorta have a solution for those cases; I toss any that don't respond to my normal treatments!

    After a couple of my "select-load-fire-reload-measure-toss the losers" cycles, the remaining brass is very good. (Wish I could shoot as good as my twice prepped brass is!)