How many times does it take to fire brass to match the size of the action?

Discussion in 'Reloading Forum (All Calibers)' started by BMG, Mar 2, 2011.

  1. BMG

    BMG

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    Another newbie question I'm afraid! I was wondering how many times it is necessary to fire (starting with virgin brass) brass so I can match the internal dimensions of my action/barrel? Once I have arrived at the maximum dimension of the cartridge then I am assuming I need to bump the shoulder back 0.001" and make sure the neck doesn't get too long? Am I correct in my assumption? Always very grateful for the advice I receive!
     
  2. Yellow11

    Yellow11

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    You haven't mentioned what round this question relates to.., but assuming it is a standard factory load and you are loading full strength charges, then once should be enough. In fact, even for a wildcat round, once should be enough.

    No need to bump the should back, unless you want to. You should only NEED to bump the shoulder back when the bolt get sticky.
     
  3. dreever

    dreever Gold $$ Contributor

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    What you are doing is matching the brass to the chamber not the action. I'd say after the second, or the third firing that's going to be as close as it will ever get. A lot of guys wait till the brass gets a bit sticky before bumping the shoulder. Myself I now bump every time just to keep things uniform.

    Danny
     
  4. artbosco

    artbosco

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    Within the wonderful world of short range Benchrest, Fireforming TWICE, is usually the norm, before introducing the brass to the competitive environment.

    Full Length sizing, each and every time the case is reloaded, is the standard followed my most competitors.
     
  5. ChipEckardt

    ChipEckardt

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    For what it is worth, when I had a custom full length resizing die made they wanted me to fire a new case three times. After each of the first two firings I was told to neck resize only. After the third do not do anything but send the brass in.

    Chip
     
  6. bozo699

    bozo699

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    Danny is spot on, and so is DaveBerg and Chip is also correct.
    You can prove this as well if in doubt. Fire a case then measure with a case comparator and dial or digital indicator, write the measurement down, keep repeating the process until your reading doesn't change anymore. A large case full of powder and a heavy bullet touching or jamming the lands probably won't take more than once or twice, a smaller case with less powder and a light bullet with a lot of freebore may take several firings to stop growing.If you really want to know for sure have your smith cast your chamber.
    Wayne.
     
  7. 338Lapua

    338Lapua

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    I only bump when the case start to get tight, then body size using comp shell holders....3 fire formings for optimal case to chamber fit for me.
     
  8. BMG

    BMG

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    Hi all

    Many thanks for the replies. I have a custom made 30-06, .243 and 22/250. I am now at the stage where I have once fired all the virgin brass for the various calibres. I am using a Redding type S Match full length neck bushing die so I am assuming I just need to full length size so I obtain the correct neck tension but do not bump the shoulder back of the cases prior to the second round of firings, or until the brass becomes sticky? Am I correct in my assumption?
     
  9. tripcrow

    tripcrow

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    Since my guns are at the smiths waiting on tooling, here's the long of it.

    Like with so many other things in shooting your question is a personal thing that has to do with your level of satisfaction. While competitive benchrest shooting often comes down to the last person that screams “F*** it. That's good enough.”. Other disciplines are more relaxed and you'll find some even have peer pressures against going to a another shooting disciplines extremes. So... without bringing annealing into it I think you're going to find that brass that's only been fired a couple of times is going to show less uniformity than the same lot of brass that's been fired many times. Depending on how stout a load you shoot, after just a few firings you may find some of the cases will start to close tight because they haven't sprung back to the same size as the others. This'll happen even if every case has been fired with the same load the same amount of times. So to compensate for this and keep cases more uniform in size, guys will full length size (Ah, but what does this mean?) every time. On a side note, if you don't FL size every time you'll find that cases will start to close hard in greater more uniform numbers as the amount of firings on them increases.

    But the thing you want to look for here is the match between your dies and the rifle chambers. And I don't mean just the right shoulder bump. Take micrometer readings at a couple places on the body of a piece of brass that's been fired with a real good heavy load. Now re-size that brass using your FL die set for a .001” shoulder bump and take readings again from as close to the same place as your previous fired case readings. You want to see a change in the .001”-.002” range. A little less near the base is great, a little more at the body/shoulder junction is no big deal. What you don't want is to find is that the case is getting squeezed down excessively or not at all. If you have a tight custom chamber you may find your non-small base Redding die isn't even touching the base of the case and is overly working the upper body.

    If the readings don't match up to your satisfaction you have some options. Get a custom or semi-custom die made. Or get a Forster bump die. The Forster won't produce as uniform body dimensions as a FL die will. But it will cut down the need to FL size dramatically. You can also try other brand commercial dies to see how close they are to your chamber. Remember, small base dies will have a tighter base.

    One other thing I find very few people talk about is the headspacing of a bushing die. By design a FL bushing die doesn't touch the upper shoulder or the lower neck. Using a 6BR bushing die on 22BR exaggerates it. What that means is that your case is headspacing on the upper shoulder that isn't being bumped by the FL bush die. Because it is so little it is hard to feel by bolt closing. If you don't believe it try FL bush sizing brass fired in a different chamber. Often times it just won't work because you're not getting the shoulder neck junction. Many times you'll need to make the initial sizing with a real FL die. Don't think a FL bushing die is totally eliminating the lack of uniformity between your brass. Better than a Wilson neck die? Yes.

    So to get a total uniform sizing you can have Forster do your neck to match your desired tension. But then you lose the lower neck acting as a centering aid. Or you can have a FL bushing die made to exactly match your neck. How much does it matter? How long can you go without saying “F*** it!”?

    Edit: By base of case I mean the spot on the body above the extractor groove.
     
  10. RonAKA

    RonAKA

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    Based on measurements I have taken I think you are at about 95% resized after one firing, and virtually 100% on the second firing.
     
  11. bozo699

    bozo699

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    On a open forum?.... I hope forever.
    Wayne.
     
  12. 1shot

    1shot

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    BillSlattery has it nailed.
    Some cartridges need once, other several. It also depends on the mfg. of the brass. For instance, we have all concluded that Fed. brass is soft. In this instance, it should form on the 1st firing. If using Lapua brass, use a stout load while jamming the bullet 15-20 thous. should do the same thing. My shooting partner and I shoot the same cartridge from different actions and different bbls. Our load varies .5 of a grain. As always, proceed with caution, but load them to the upper end, and jamb the bullets, and you will have good consistent brass with the 1st firing. BTW, if you have a chrono available, shoot those loads through the screens an weed out the powders that don't show promise.
    I hope this helps,
    Lloyd
     
  13. BMG

    BMG

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    I am using Lapua brass for my 30-06 and .243 and Norma for my 22/250.

    Thank you guys for your very valuable input, it is greatly appreciated.
     
  14. Aussie_bob

    Aussie_bob

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    Remember to check over all length of brass after each fireing to see if it has grown any and trim for clearance On first firing some cases actually get shorter as the blow the shoulder out.
     

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