runout problem with sizer die

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by rufous, Jun 13, 2002.

  1. rufous

    rufous Well-Known Member

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    I am having a problem with my Redding neck sizer die. It is giving me more runout than I would expect it should. Press is a RCBS Rockchucker. I am using an o-ring on the die so that it “floats”. I had heard that the o-ring can help to reduce runout. I have not tested it with the standard lock nut. Fired cases have less than 0.001” of runout on the neck. They have less than 0.001” variance in neck thickness as well. But when I run them through the die (it has a carbide sizer button) they come out sometimes with 0.0035” of runout. 0.003” is common. I removed the carbide button and runout was still about 0.00275”. I use moly powder when neck sizing. I cleaned the die with a q-tip and checked again and runout was still about 0.003”. So what might the problem be? I have heard that as runout increases so will group size. Is there any ballpark figure? Like if the gun shoots 0.5” groups with 0 runout what would group size be with 1, 2, 3 thousandths of runout? Thanks, Rufous.
     
  2. Brent

    Brent Well-Known Member

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    Have you marked the cases with a marker to see if the runout is happening all on the same side of the die? It may be off bored?
     

  3. milanuk

    milanuk Well-Known Member

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    Rufous,

    You didn't say which neck sizer, the Competition or the Type 'S' die. I've used the Competition dies in .223 and .220 Swift, and had no problems, since I normally neck turned the cases being used. I'd end up w/ loaded rounds w/ about 1-2 thou runout, ususally less. On the other hand, when I picked up my 700VS in .308 Win, I got a Type 'S' die, since in all honesty, I for one don't ever use the micrometer set on the Competition die once it's been set up initially. I was getting up to 10 thou run out on loaded rounds, and eventually backtracked the problem to the neck sizer giving me at least 4-5 thou at the neck, which for a variety of reasons ended up magnified on the loaded round runout. I had the standard sizing button, but even w/o it, I still got what I considered too much runout. Redding gave me some song and dance about sizing the brass down too much because of a sloppy factory chamber causing the runout. Yada yada yada.

    My solution? It sounds hokey (and feels cheap as hell), but the Lee Collet die saved the day for me. I inadvertently ordered the whole 3 die set, but just the collet die costs something like $16 or so. I figured it was cheap enough to take a chance on.

    My inital loads, w/ the Redding dies, were shooting about 3/4-1"@100yds, 1-1 1/4"@200yds, and 1 1/4-1 1/2"@300yds w/ the 175gr SMKs over 45.0 gr varget. Basically the bullet needed some time to stabilize itself and overcome the initial yaw from going into the rifling crooked due to the runout, I believe, as the loaded rounds had like I said, up to 10 thou runout. My followup rounds loaded w/ the Lee Collet die, have about 2-3, sometimes 4 thou TIR, and routinely shoot under 1/2"@100yds, w/ one 3-shot group punching a nice .40-.45 caliber hole [​IMG]

    A few things to note: I haven't ever used the O-ring btwn the die and the press trick, more out of laziness in finding a suitable O-ring than anything else. The Lee Collet die does come w/ one installed, IIRC. I do however 'float' the shell holder, by removing the metal clip, and (again, since I am too lazy to hunt down an O-ring) wrapping a rubber band around it a few times to retain it, so it isn't being pushed one way or the other by the metal clip ring. Also of note: I initially didn't notice much reduction in runout in the cases necks themselves using the Lee Collet dies. I did however, notice a substantial improvement upon measuring TIR of a loaded round. My theory about this is as follows: The bushing dies work fine... if you neck turn. When I neck turn, I expand the necks first w/ a mandrel, to 'iron' any deformities to the outside surface of the neck and then use the cutter to reduce/eliminate those irregularities. Subsequently when the neck bushing dies squeeze the neck down, effectively ironing the neck in reverse, there isn't much in the way of irregularities or variations to transfer to the inside neck, and the bullet/neck junction, so TIR is low. If you don't neck turn, the bushing die irons any defects to the inside of the neck, where they are magnified in TIR of the loaded round. The Collet die forms the neck around a solid mandrel, effectively ironing the defects to the outside of the neck. Hence, you don't see much improvement in measuring the outside of the neck for runout, but when the bullet is seated, and loaded round TIR is measured, a noticeable benefit is realized.

    These are simply my observations. I am by no means an expert, and your mileage may vary. If you try the above, and your stuff breaks, you get to keep both parts [​IMG]

    HTH,

    Monte
     
  4. Delta Hunter

    Delta Hunter Well-Known Member

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    milanuk, it doesn't sound hokey to me. I never could get runout down to an acceptable level with the Redding S neck dies, so I gave the Lee Collet neck die a shot. Boy does it work. I'm now getting runout of .001 or less measured on the seated bullet. I haven't touched my Redding dies since buying the Lee Collet neck dies.
     
  5. Guest

    Guest Guest

    Rufous,
    I had same problem with one of the Redding dies also, the neck on the '06 case was being pushed out 6 thousands, sent die back and it took 5 weeks to get it replaced. Will buy no more.
     
  6. speedbump

    speedbump Well-Known Member

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    Same thing with a Redding die in 7mmRUM. 6-15/1,000. [​IMG] I went to a standard RCBS die & it's consistently 1-3/1,000 now. Sounds like a trend... [​IMG]
     
  7. milanuk

    milanuk Well-Known Member

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    Delta Hunter,

    I didn't mean that it *sounded* hokey, I meant that from my experience, the Lee Collet dies are about the chintziest feeling things I've yet to run into. But they work, so what the heck.

    Monte
     
  8. Nicholas

    Nicholas Well-Known Member

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    Have you guys had any runout problems with the Redding competition dies or with just the S dies??? I just got the comp dies and you are starting to worry me. [​IMG]
     
  9. speedbump

    speedbump Well-Known Member

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    SR90,

    Mine are 'S' dies. I'll be sending them back with a note.... [​IMG]
     
  10. Nicholas

    Nicholas Well-Known Member

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    I tested my competition dies today and everything works great.

    Sorry to hear about your bad dies.
     
  11. Guest

    Guest Guest

    I would like to add one thing that I have done to help the "run out". I run the casing into die to knock out primer, then extact casing half way, rotate casing half way and resize again. This alot of times will straighten the neck out. Just give it a try.
    I will also seat the bullet 1/4 way, then rotate casing half turn and finish seating. This has made a big differnce in run-out for me.
    My Redding die was the standard die.

    [ 06-25-2002: Message edited by: Coyote Hunter ]