Concentricity - setting up dies - runout

Discussion in 'Reloading' started by dig, May 3, 2011.

  1. dig

    dig Well-Known Member

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    I just ordered a Hornady Concentricity Gauge. I keep reading about setting up dies correctly to minimize run out. So how do you set up dies differently? Granted I don't have results from measurements yet but want to understand how to tweak dies for minimum run out. Thanks
     
  2. boomtube

    boomtube Well-Known Member

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    Hornady's Concentricity gage has a way to hopefully bend a round straight. Okay. But I don't care for bending anything to correct an error, rather use my gages to find where the non-concentricity comes in an fix it there.

    Several things contribute to runout, I've never found "die set up", as such, to be a big issue.

    Bad case necks, that is non-concentic necks, is the biggest factor. If the necks aren't straight no die can make them so. For factory (loose) chambers, lightly skim turning necks will improve the consistancy but making the mecks too thin adds it's own problems to the already loose fit.

    It helps if the expander ball is bullet diameter or no more than a thou smaller. Most sizers squeeze case necks much too small and then we drag a short expander ball back out. That extraction pull tends to drift to the thin/soft side and pulls a formally straight neck to an offset angle; not good! Using an outside expander die/plug that pushes in rather than out, such as Lyman's "M" expander helps a lot.

    Excessive 'bullet tension', any more than maybe 2 thou, frequently causes bullets to tilt during seating. No presumed tricks such as seating part way, turning the case and completing seating can do anything significant to reduce it either, the die's internal fit is usually too loose for that to really matter.

    I LOVE Lee's collet neck sizers, they do not make the necks too small (So, some owners insist on grinding the inner mandrel down to make it so!). The collet fingers work to make the ID correct for best seating AND does it in such a way as to leave the sized necks about as straight as the brass itself will permit. The Lee collet has a moving part and that seems to buffalo some users but anyone willing to learn to use it correctly will be happy.

    When I need to FL size my precision cases I use a body die and finish with the Lee Neck Die.

    It is possible to use a "bushing" type neck die but all that can do is make the external neck diameter consistant. If the necks are not turned to a consistant thickness the difference will be forced inside and that will cause variation in bullet grip and that is NOT good for accuracy! Many bushing die users want a 'high bullet tension' (more than 2 thou,) and that increases the average runout from seating in a too tight neck.

    With good necks, properly sized, a really good seater finishes the job. ONLY the Forster BR and Redding Competition dies have a "staight line" seater design. Their heavy inner spring loaded guide sleeve fully contains both the bullet and case in line before seating starts. (The various micrometer type seating heads are user helps only, they do nothing to make the ammo straighter.)
     
    Last edited: May 3, 2011

  3. Gene

    Gene Well-Known Member

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    May 3rd, 2011
    Try Using O-Rings with Sizing Dies for Reduced Neck Run-out
    Here’s an inexpensive procedure that can help you load straighter ammo, with slightly better measured concentricity (i.e. less run-out) on the case necks and bullets. Simply use a rubber O-Ring on the underside of the die locking ring. This allows the die to self-align itself (slightly) to the case that is being sized. Without the O-Ring, if the flat surface on the top of your press is not perfectly square with the thread axis, your die can end up slightly off-angle. This happens when the bottom of the locking ring butts up tight against the top of the press. The O-Ring allows the die to float slightly, and that may, in turn, reduce the amount of run-out induced during case sizing.



    Top prone shooter German Salazar has tried this trick and he says it works: “Go to your local hardware store and get a #17 O-Ring (that’s the designation at Ace Hardware, don’t know if its universal). Slip the O-Ring on the die and re-adjust the lock ring so that the O-Ring is slightly compressed when the die is at the correct height. Size and measure a few more cases. You will probably see a slight improvement in neck concentricity as the die can now float a bit as the case enters and leaves it. This isn’t going to be a dramatic improvement, but it’s a positive one.” We want to stress that adding O-Rings to sizing dies may help some reloaders, but we don’t offer this as a panacea. Try it — if using the O-Ring reduces measured runout that’s great. If it doesn’t, you’ve only spent a few pennies to experiment.



    Lee Precision makes die lock rings with built-in O-Rings. Lee’s distinctive lock ring design allows the same kind of self-alignment, which is good. However, Lee lock rings don’t clamp in place on the die threads, so they can move when you insert or remove the dies — and that can throw off your die setting slightly. By using an O-Ring under a conventional die lock ring (that can be locked in place), you get the advantages of the Lee design, without the risk of the lock ring moving.
     
  4. boomtube

    boomtube Well-Known Member

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    Gene raises a good point about the effect of O rings under the die lock nuts. It's intuitive for most of us that it should be great if we use a wrench to lock dies down hard; it's NOT! A hand tight die is plenty tight and even that can be over done. I've taught my right hand to be consistant in installing each die to a snug but not hard fit; that alone allows for a bit of mechanical slack in the mounting even without rubber rings.
     
  5. RDM416

    RDM416 Well-Known Member

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    I agree with everything Boomtube said, very good advice....... except this part. Everyone may not see improvements with this method, but I sure do. I will typically size using about 7 or 8 partial strokes, then do the same with seating the bullet, taking special care with initially starting the bullet in the neck. I will lightly "tap" the bullet, then rotate and "tap" again with ever increasing pressure until the bullet gets fully started in the neck. Then I go ahead and seat it with one or two more strokes.

    While I do load for several calibers, most of my loading is done for a couple of custom rifles using custom dies made by the rifle maker. With the EXACT same set up I can size and seat using a single stroke each and my runout will about .003 to .004 on average. I can use the method described earlier and reduce the runout down to LESS than .001 on 80% and no more than .002 on the rest.

    One of the most respected smiths on this site suggested I try this a few years back when I was struggling to reduce runout. (don't wan to drag him into this or I would mention his name)

    The way it was explained to me is that every die has some error however slight, and the same goes for every press. When you rotate the case during sizing or seating, you are spreading that error out over several points rather than all the error being in one direction.

    I am not a machinist, so I am not going to claim I really understand fully how or why this works. I do know it works for me. I am skeptical enough to keep trying to prove it wrong. In the middle of loading 20 rounds I often take 1 and just size and seat in a single stroke, runout will almost always be at least (often more) .002 more than the rest of my loads. I will also admit to being a little "obsessive" about runout. Many well respected shooters will say that around .003 or .004 is "good enough". My equipment is usually set up to produce that level of runout even without rotating.

    I'm certainly not trying to start an argument with boomtube, and will admit to being wrong before (only once or twice if you don't ask my wife:D) but the "rotate" method sure seems to work for me.
     
  6. dig

    dig Well-Known Member

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    All great advice, I will try the "O" ring on by Turret Press, I am thinking my Forster probably eliminates this problem anyway as the die sort of "floats" and self aligns. I am using almost all Redding Dies but have found the decapping rod/expander is never perfectly strait, will the "O" ring help with this as well, anyone tried it?

    Again, think I am am ahead of the game as I have not started measuring yet but look forward to further improving with these techniques!

    Thanks,
     
  7. Mikecr

    Mikecr Well-Known Member

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    Hate to be discouraging, but I think you've started off wrong already..
    For one, you can't measure 'runout' with the Hornady tool. So it won't help an endeavor to reduce runout.
    You should have gone with a Sinclair concentricity gage(which is actually a runout gage) instead. It would have been the same cost: Sinclair Search : Reloading Equipment : Measuring Tools : Concentricity Gauges -
    Or the NECO, but it cost a little more.

    There are very important differences, which will be completely hidden from you using that Hornady...
     
  8. boomtube

    boomtube Well-Known Member

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    RDM: "The way it was explained to me is that every die has some error however slight, and the same goes for every press. When you rotate the case during sizing or seating, you are spreading that error out over several points rather than all the error being in one direction."

    Yeah, it sounds reasonable, and I sure won't say it NEVER happens, but it's not normally very effective. I've tried it on too many dies of different designs to belive it. Once a bullet gets started crooked the mouth and neck have been 'bent' and it's hard to force the bullet to go in much straighter no matter how we may spin the case!

    Two things work against it. First, very few seaters are sufficently tight to forcefully correct any bullet that has started off axis. Consider that most seating stems are fairly long, they are usually of small diameter and the cup is only loosely fitted in the bullet bore and there simply isn't enough rigidity to the stem itself to push a misaligned bullet over the few thou required to straighten it out, and that also applies to the excellant Forster and Redding Comp seaters. Lee's very good seater bullet chambers are usually quite close to the indeal bullet diameter but it's short and the floating upper plug has no alignment force at all!

    Second, visualize what's happening, and where, inside the die when seating begins. The case necks are largely unsupported, or are often supported only by the case body wall against the die wall, when seating begins so seating is initiated with the case mouth and bullet heel hanging almost loosely in free space at the most critical moment. There is little at that point for even a truly rigid seating stem to work against if we do rotate it!

    Those few seaters with short sliding bullet guide sleeves, such as the current Hornady and RCBS Gold Metal, do a good job of making sure bullet heels enter the case mouth but that isn't much of a problem anyway! Older versions of the same design (from other makers) were dropped decades ago because they didn't seat any straighter than conventional seaters. Still don't; those very loosely fitted short sleeves are much less effective in loading low runout ammo than the Forster/Redding full length sleeve designs which totally align the case and bullet before seating ever begins.
     
    Last edited: May 4, 2011
  9. dig

    dig Well-Known Member

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    From Hornady Website. Did I miss something?


    The Hornady Lock-N-Load Ammunition Concentricity Gage is the first tool on the market to both identify and eliminate bullet runout. Bullet runout can be caused by a number of different variables in the reloading process and can effect the accuracy of loaded ammunition. By identifying bullet runout and eliminating it ammunition becomes more consistent leading to better accuracy. Just place loaded ammunition in the tool, roll it and identify runout on the dial. Once runout is identified the dial indicator is used to adjust runout to zero. This tool will work with both reloaded ammunition and factory ammunition to eliminate bullet runout and make it a thing of the past.

    Technical Information


    Type: Concentricity Gage
    Function: Identify and Eliminate Bullet Runout
    Accuracy: .001"
    Range: 0-1"
    Warranty: No-Risk, Lifetime Warranty
    Notes:
    Max Cartridge Length 4"
     
  10. Mikecr

    Mikecr Well-Known Member

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    Yeah,, you've missed the fact that Hornady will say anything -to sell their copies of other peoples products(in red) -to you..
    It's not a runout gage, but a concentricity gage.

    "The Hornady Lock-N-Load Ammunition Concentricity Gage is the first tool on the market to both identify and eliminate bullet runout"

    In truth, IT DOES NEITHER, and it is not the FIRST adjusting concentricity gage on the market..
    Their statement here is also as ignorant as untruthful.
    'Bullets' are not cartridges, or loaded ammo. They are merely the projectiles.
    Nothing can eliminate runout in these, once finished, other than a lathe.

    You might think it's a nit picking play on words. But if you're to reduced actual ammo runout, you'll need to be critical of details along this line.
    If your real desire is to reduce eccentricity, then you should be asking about that.
     
  11. boomtube

    boomtube Well-Known Member

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    "It's not a runout gage, but a concentricity gage."

    That's a presumed distinction without an effective difference. Bullet runout IS cartridge non-concentricity. ??

    I like the Sinclair gage and have no personal interest in the Hornady tool but I can't see how the end results of the red version would be any different in application.

    While you are technically correct that Hornady's tool is not the first to allow jacking/bending a neck & bullet into better alignment, they ARE the first major reloading supplier to provide such a tool and I'm sure that's what they mean to say. If you seriously reject all manufactors because of a bit of advertizing blarney and some self promoting hyperbole, you wouldn't have anyone to buy anything from!

    Chill. :D
     
  12. Mikecr

    Mikecr Well-Known Member

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    Well, BULLET runout is below measure for most of us(without a juenke).
    But,, a cartridge can have all shapes and sizes of runout and still be perfectly concentric.
    Conversely, very low runout ammo must be concentric.
    So they are completely different things.

    Because you haven't recognized the differences between Sinclair and Hornady.
    Apparently, many don't.
     
  13. RDM416

    RDM416 Well-Known Member

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    boomtube, You and I pretty much agree on this...... I do not propose the "rotate" method will fix large or even moderate amounts of runout. All the the other things mentioned, O-rings, leaving dies a little lose, etc are all tricks in my toolbox for minimizing runout. My normal setup uses a Forster co-ax press for sizing with a custom die, then seating with a Redding competition die on an RCBS press.

    I think the most important part of my process is the "light tap on the bullet, then rotate and repeat several times". This seems to be quite effective at getting the bullet started straight. All the rest may actually be overkill. I certainly agree that once the bullet has gotten started crooked (at least more than 2 or 3 thou) that there is little that can be done (in the die anyway) to fix that.

    To sum it up...... My experience with this shows me I can take an already good, .002 or .003 runout setup and reduce it by .002 or so. I agree you are not likely to fix larger issues doing this, and it is certainly not a cure-all for runout issues. This method is certainly not a fix for bad dies or a sloppy setup, simply a fine tune for already good loads. IMHO.

    +1 on the Sinclair concentricity gauge.

    dig, See this little "discussion" between boomtube and I? If nothing else, you can learn from this that although the basics remain the same, you will in time develop your own style of loading. Some get real picky about runout, some about weighing powder, some with bullet and case sorting, neck tension, etc........ Some are picky about all of it. At the same time you can find someone (who is a very good shooter) who will say that one or the other of those things don't matter enough to bother with and they don't do it. I am usually not in a hurry when loading so I take the time to control as many steps with as much precision as possible. In the end, all error is additive. One small bit of error in one step may not matter, but fixing that one may make up for the one you did not or could not fix.
     
  14. boomtube

    boomtube Well-Known Member

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    "I think the most important part of my process is the "light tap on the bullet, then rotate and repeat several times". This seems to be quite effective at getting the bullet started straight. All the rest may actually be overkill. I certainly agree that once the bullet has gotten started crooked (at least more than 2 or 3 thou) that there is little that can be done (in the die anyway) to fix that."

    Okay, that's not been my experiece but I have't tried THAT small a start! I can accept that it works for you.

    Wonder if you've ever tried Lyman's "M" expander dies? Properly used, they will open the mouth enough to allow bullets to drop in that first few thou and can provide a better start. Plus, since it expands on the way in, the M's long expander section tends to produce straighter necks than any ball expander can do. I did my expanding that way for a several years before I started using Lee's Collet Neck Sizer and a body die for all of my sizing work.