Help! Case neck runout...bent decapping rod?

Discussion in 'Reloading' started by orch, Sep 27, 2011.

  1. orch

    orch Well-Known Member

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    Looking for some recommendations from some more experienced reloaders here...

    I was prepping some new Lapua 308 brass today and I was running them all through my rcbs fl competition die to fix the necks cause some of them were dented and out of round..
    I noticed the case neck run out was going from 0 to 1 thou presizing to 10 to 15 thou post-sizing! So after banging my head against the reloading bench screaming WTF! I pulled the die apart and took a look at things but couldn't see any obvious problems... So I tried sizing a couple pieces without the decapping rod/expander button and low and behold the runout was back down to 0-1 thou.. Put the expander back in and it was right back to 10-15 thou... Didn't matter if I ran the expander right up close to the neck of the die or right down near the case head, or had the rod free floating or clamped tight with the locknut... Lube in the inner surface of the neck didnt help...
    So now I'm pretty sure the decapping rod is bent....
    What should I do? Order a new decapping rod and wait god knows how long to get one in the mail? Just bite the bullet and spend $100 bucks or so and get a bushing die set from redding and again wait for delivery?
    Or, since I am loading with vld boat tails can I just let the bullet do the neck expansion for me?

    Is this gonna run me into neck tension problems if I do this?

    Thanks in advance for any insight...


    Orch
     
  2. Gene

    Gene Well-Known Member

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    Remove the expander from the decap rod. Lay the rod on a flat surface and roll it slowly. You should be able to see a small wobble if it is bent. A bent decap rod will definitely cause run out. Call RCBS and they will send you a new decap rod for free.

    The expander is your worse enemy, and puts much stress on necks, in addition to frequently causing run out. Get a bushing die.
     

  3. boomtube

    boomtube Well-Known Member

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    Get a Lee Collet Neck Die and get good necks without fiddling with gimmics.
     
  4. Broz

    Broz Well-Known Member

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    Here is my experience over many years of reloading with many die types.

    All expander balls have induced runout for me. However if the die is custom ground for your brass to only down size a limited ammount it will be better. Or you can simply adjust this with a bushing die by selecting the proper bushing. Also the option of not using an expander at all is a good choice the bushing die will allow.

    With the Lee collet dies I have used I had problems getting enough neck tension. This was an issue even after many attempts to get it properly adjusted. Maybe I needed a smaller inside mandrel but I could not get a good feeling about the vertical creases the Lee collet leaves on my case necks so I went to the bushing dies and have found them to be awesome.

    I size in two steps. First the necks where I get consistant neck tension of .002" Then I use a body die that alows me to size the body and only bump the shoulde back about .0015"

    The result is very consistant cases both in neck tension and with all the shoulders at the same place. Which allows for very consistant bolt closure and opening after firing even in warmer weather.

    My total indicated runout of a loaded round, checked at the o-give of the bullet, averages .0005" to .001" and more are to the lesser side of that.

    Many ways to skin a cat, but this is working well for me and my ES and ELR groups are as tight as I have ever had.

    Jeff
     
  5. orch

    orch Well-Known Member

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    thanks for the replies guys.....

    Gene... i took the decapping rod and rolled it in my concentricity gauge and i was getting about 2 thou runout on the expander button (round carbide button that sits about an inch above the decapping assembly) it wasnt obvious to the naked eye.... cant understand how 2 thou on the expander translates into 10 to 15 on the neck but i digress....

    so that is two votes redding bushing dies and one vote lee collet die, and i take it a NO on just using the FL die without the expander and letting the bullet do the expansion ( :rolleyes: dang i was hoping i could get away with that atleast in the short run as i wanted to get up and running with the new lapua brass right away) oh well i will just wait till i get back to the city and see if the guy i usually get my redding stuff from has a set of bushing dies....

    i have heard good things about the lee collet dies from guys but have never used one before and to be honest the only lee dies i have used i was less than impressed with... they were just the regular lee dies in 223 my cousin got for his gun and he got them because they were the cheapest.

    i am not too sure i want to go the route of neck sizing then running them through a body die to bump the shoulder in a two step process so i guess a redding series A full length bushing die would be the way to go....

    thanks

    orch
     
  6. Broz

    Broz Well-Known Member

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    Yes, get the FL bushing die and if you ever get the urge to try the two step process you simply buy a comp neck bushing die and take all the guts out of your FL die you already have, and it becomes a Body only die. If you study the difference between the plain FL bushing die and the Neck die you will see that the comp neck die fully captures the case in a retractable sleeve before it sizes the neck. This I feel keeps everything true to the bushing and the result is straighter necks.

    I should also add with the two step method you have the option to only neck size in one easy, no lube step using a titanium bushing. Until the shoulders grow to the point they do need bumped.


    Also I might suggest you try this with your present die. Leave the expander stem loose with a small O-ring under the lock nut only finger tight. Then lube the inside of the necks a bit. This will allow the stem and expander ball to self center upon extraction. It may help. But will add the step of cleaning the excess lube out after.

    I feel the reason you are getting this runout is from the die oversizing the necks down. Then the expander gets pretty hard to extract through your necks. Also if the necks are not consistant in thickness all the way around, the neck puls to the thinner side and induces a pulled crooked neck.

    Jeff
     
  7. orch

    orch Well-Known Member

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    jeff i think you are dead on in your diagnosis of my problem! i measured the OD of the necks on some sized cases without the expander and i am getting about 5 thou smaller diameter than with the expander in... so i am guessing the brass is getting moved 8 thou or so when you take your sping back of 2 thou into account each way... so yah that die is squeezing that brass down quite a bit... and it does take a bit of a pull to get that ram back down as the expander pulls back out...

    i switched to the lapua brass in the 308 because i was impressed with my 338 lapua brass's neck thickness consistancey so i hope it isnt inconsistent neck thickness (i was really hoping to avoid having to neck turn this stuff)

    i did try the die with the stem loose and with lube in the inner neck and it showed no improvement...

    only neck sizing is pretty much what i am doing with my fl die as it is... its a savage that i swap barrels in and when i set the headspace when i put the barrel on i headspace it to minimum speck so the fl die was only bumping the shoulder back about 1 thou from the fired case dimension... so i may as well just go with a fl bushing die.... i have one for my 338 lapua and have been really happy with it so i may as well just follow suit with the 308....

    orch
     
  8. Broz

    Broz Well-Known Member

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    Bingo!!! Kinda hard to argue with success.

    Jeff
     
  9. Trickymissfit

    Trickymissfit Well-Known Member

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    one of the problems with the expander button (ball or whatevery you want to call it) located just above the decapping pin is that the case neck is unsupported when it sized. That means it can be anywhere when the button is pushed thru it. A Forster die has the button located much higher, and sizes the neck when the case in encapsulated in the die body; making everything much more concentric. I don't know if that's the problem, but think it's worth a look after you said that the necks are fine without the expander button in place.
    gary
     
  10. orch

    orch Well-Known Member

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    Hey Gary, I thought of that too... I ran the expander up so it was about one thread from the case neck while the case was fully in the die so the expander was starting to do it's work while the upper part of the neck was still in the neck portion of the die and it still gave me pretty bad run out... About 8 thou....

    The rcbs competition die in question has the carbide expander higher up on the decapping rod assembly and separate from the actual decapping pin holder unlike the conventional rcbs dies... Probably similar to how you describe the Forster dies (I have never used a Forster so I can't say for sure)

    on a side note I realized I had a regular 30-06 rcbs die that I have hardly used so I stole the convetional decapping/expander rod from it and the case neck run out went back down to 1-2 thou.... But I think I will still switch to a bushing die to reduce the amount I am moving the brass back and forth with each resizing cycle...

    Orch
     
  11. Trickymissfit

    Trickymissfit Well-Known Member

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    I think you proved your question. The stem is probably bent or the actuall expander button was made with some error in it. .004" concentricity error will give you .008" runout, and that's hard for us to see with the naked eye. Try leaving the stem loose in the die body and see if that helps you.
    gary