straightness

Discussion in 'Reloading' started by bota, Feb 21, 2010.

  1. bota

    bota Well-Known Member

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    I recently purchased a sinclair run out gauge, and found out that all of the rounds i am loading are very crooked. I thought that the problem may have been my seating die, so i got a forester bench rest seating die. This didn't help. I am using a brand new rockchucker press, and its operation seems to be good.

    When i measure my fired brass, there is usually <.001 run out on the neck. After running the brass trough my sizing die, run out increases to ~.002 or .003. Then run out increases to .004 to .008 on the seated bullet when measured close to the neck.

    I am not sure how to fix this, but i am thinking that a better sizing die would help? What would you guys do?
     
  2. britz

    britz Well-Known Member

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    Much of runout is caused by the expander ball in the resizing process. You may want to use some extremely fine grit sand paper or wire mesh and polish the ball to reduce the friction.
     

  3. Winchester 69

    Winchester 69 Well-Known Member

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  4. bota

    bota Well-Known Member

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    thanks for the replies. I will try the suggestions in the expander ball thread. Is the small amount of r.o. introduced in the sizing stage leading to the massive r.o. after the bullet is seated?
     
  5. trueblue

    trueblue Well-Known Member

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    bota,
    just resize without the expander ball, but make sure you check how much neck tension that gives you.
     
  6. Moman

    Moman Well-Known Member

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    Bota, what kind of sizing die are you using?
     
  7. bota

    bota Well-Known Member

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    RCBS sizing die. How do you check neck tension?
     
  8. Moman

    Moman Well-Known Member

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    Bota, you can unscrew the stem with expander ball out of your die and resize a case. This will show you how much your die sizes down the neck without the expander ball expanding it back. Take a measurement at the neck. Measure another neck of a loaded round. That should show you your neck tension.

    I still use expander balls in my FL dies, old habits are hard to brake. The ones I have been buying over the last couple of years have been the Forsters. They have a rubber washer under the stem lock nut, this allows a little bit of flex in the expander and helps it align better with the case, in theory to reduce expander induced runout. Also, the expander on the Forster is mounted much higher on the stem so it engages the case neck while the case is still supported in the die. For a $10 service fee, Forster will hone the neck of their FL dies to reduce some of the neck tension. Again, this helps with reducing expander induced runout as well as overworking the case in this area.
     
  9. trueblue

    trueblue Well-Known Member

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    bota,
    if sizing without the expander ball gives you to much neck tension, say .006-.008 you might want to look at a fl sizer bushing die and use the appropriate size bushing to control neck tension that way. I am just not a fan of using the expander ball on fireformed cases.
     
  10. Mikecr

    Mikecr Well-Known Member

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    Good move. Broke is halfway to fixed.

    This is very common. Brass is as good as it’s ever gonna get, right out of the chamber. Anything we do screws it up from there. But it’ll get a lot better when the bugs are worked out.

    Probably true.
    Two things I predict; Your brass has a lot of thickness variance,, Your die is over sizing.

    1. Pick up a Sinclair neck thickness gauge(ball mic with stand). Cull out high thickness variance brass. Someone on a similar thread says he’ll take it.
    2. You can send a few freshly fired cases and a Redding body die for your cartridge to JLC Precision. Jim will make you a FL bushing die that will not oversize.
     
  11. trueblue

    trueblue Well-Known Member

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    I have used JLC Precision on a few dies.
    Good recomendation by Mikecr.
     
  12. Bart B

    Bart B Well-Known Member

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    I'd buy a Redding or RCBS bushing die that full length sizes cases with out bending necks with an expander ball. They both use the same bushings and use a bushing whose diameter's 2 thousandths smaller than a loaded round neck diameter. Bushings cost about $12 each so one can get two or three for different neck wall thicknesses their brass has. This is what Sierra Bullets uses to full length size all their cases that such dies are available for in their bullet testing operations.

    These dies will size case bodies fired in standard SAAMI dimensioned chambers such that body diameters are reduced no more than 2 or 3 thousandths. That's all that's needed. As the case body's well supported when the neck is sized down just enough so its springback will allow about a thousandths interference to the bullet, case necks will be very straight.

    A friend tried his regular RCBS .308 Win. full length die without the expander ball to size cases and found bullets were very hard to seat. That death grip on the bullet caused enough higher pressure to extrude brass at the case head well back into the bolt face cutouts and swell the primer to near 1/4th inch in diameter at the edge of its pocket in the case.

    If your chamber's on the big side of specs, you may have to spend more for a custom die made for your chamber so the fired cases aren't sized down too much. Alan Warner's one who makes excellent ones: Warner Tool Company - Reloading Dies. It's not important that the full length sized case have exactly the same body and shoulder taper as the chamber does. While such things are possible with expensive custom made dies, most of the time they're not needed.

    Folks used to just lap out the necks of regular full length sizing dies. I've got six .308 Win. full length RCBS dies with necks at .332" through .337" depending on what brass I use. I don't turn case necks unless they've got more than 1 thousandths spread in thickness.

    Redding's web site has quite an article on what causes bullets to have a lot of runout. It boils down to one thing; the case neck has to be aligned well with the case body axis before the bullet's seated.
     
  13. Buffalobob

    Buffalobob Writers Guild

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    Measure it at the same place on the neck both times.

    If your neck is out 0.003 then simple geometry says your bullet when seated will be out more than 0.003.

    Couple of standard, cheap, no money spent, fixes to try. They may not work but they are free.

    1. Take the retaining pin out that keeps the shell holder in place and let the shell holder float. You can put a rubber band or O-ring there is you wish.

    2. Take your die in your hand and observe the simple fact that threads on the body are spiraling around at an angle. Grab the lock ring and observe the fact that here is slop and play in it so that it will spin freely around on the die body threads. Reach up and turn the switch to your brain to the "ON"' position. Think for a minute and conclude that it is possible to lock the lock ring in a position that causes the die body to not be straight up vertical. Grab three or four cases and your runout gauge and screw out the expander ball and lay it aside. Start running cases up into the die body and loosing and re-tightening the lock ring to see if you can get the die body to be vertical. Once you are getting straight necks out of the die body then put the expander ball back in and tighten it and run the cases in and see if that problem is cured. If it is not cured then try a sloppy loose expander ball and see if it will pull out straight when it is free to self center. Lube the inside of the neck to reduce binding.


    May not fix your problems but it will get you some practice setting up your press and dies properly.
     
  14. flashhole

    flashhole Well-Known Member

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    Hornady sells a tapered expander for RCBS dies. You might try one of these prior to getting a custom die made or even get another sizing die.

    You might also try aligning your existing expander to the die with a known good case. Loosen the expander assembly and the die so it's not locked, run the brass up into the die, ensure the decapping pin is protruding through the flash hole, then tighten the die then the expander assembly.

    You could also use a dry lube on the case neck. I use powdered graphite in a small container of #9 shot. Plunge the neck in a couple of times and you get enough graphite to reduce friction.