Work hardened brass and POI...

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by jmden, Oct 9, 2007.

  1. jmden

    jmden Well-Known Member

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    Hi all,

    What happens to POI, general ballistic consistency and effects to the case (if anything) with brass that has been work hardened and won't shoulder bump as it should such that there's a little extra pressure necessary to lower the bolt.

    Just curious what others may have experienced in this situation.

    Jon
     
    Last edited: Oct 9, 2007
  2. BountyHunter

    BountyHunter Writers Guild

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    Generally, your teck tension will vary greatly. Your groups will open up big time.

    Anneal it or throw it away. Only two choices.

    If you were using inline dies to seat with a KM press with dial indicator, you could measure the difference in seating force.

    BH
     

  3. James H

    James H Well-Known Member

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    ---- +1
     
  4. jmden

    jmden Well-Known Member

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    Thanks guys. I should've chambered a few sized cases to see if they chambered OK before I got ready for an all day long range session as I ended up with probably over 50% of my cases obviously workhardened and at 880 and 1018 yds, my groups were not what I had expected--a little tricky cross canyon winds that I was having trouble accounting for as well. Needless to say, the cases were annealed when I got home that night and a headspace gage showed great consistency with a .002 shoulder bump and averaging .001 concentricity after sizing, trimming and turning off the high spots again due to the trimming. Hopefully, I'll see better results next time out!

    Another question. I seem to recall some debate about this sometime ago. I know Lapua cases come annealed--it's quite obvious, but what about other manufacturers? It they do, it's not nearly as obvious and I'm starting to think that for general consistency, I should probably anneal brand new brass. Any thoughts there?

    Thanks for the input.
     
  5. CatShooter

    CatShooter Well-Known Member

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    Not true... you have been given information by someone that doesn't know what they are talking about.

    Ol' BH likes to give opinions about things he knows nothing about.

    I hope you didn't throw away your cases.

    First, ALL case makers anneal the shoulders, or they wouldn't be able to form the cases.

    Lapua (and the military) does not polish the cases after annealing, our domestic makers (and most foreign makers) do.

    Shoulders do not work harden (since they do not do any work ;) )... and the amount of bumping the shoulder does or does NOT do...
    ... has nothing to do with neck hardness, or annealing. They are two totally unrelated issues.

    The only time you can work harden shoulders is when you are forming wildcats and moving shoulders back with form dies, and even then, "hardening" is rare.

    The reason that your cases don't "seem" to bump, is because chambers and dies have an allowable tolerance - it's the ol' +/- 0.00xx thing.

    In your case, you have a chamber that is on the short side of the allowable tolerance, and a bump die that is on the long side. So the die is not capable of bringing the case down that last few thou that you need.

    There is probably just a few thou difference... and a few strokes of the press can make them fit ("multi-bumps").

    If you cannot get the cases to fit, the die maker will adjust the die for free.

    As too annealing - there is no reason to throw out brass even if the shoulder is hard - it anneals just fine - all brass is annealed at the shoulder to start with.

    And lastly... ballistically, brass that fits the chamber tightly is more ballistically uniform, than brass that is loose in the chamber.

    None of it has anything to do with necks or neck hardness, or annealing necks.

    .
     
    Last edited: Oct 11, 2007
  6. dwm

    dwm Well-Known Member

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    Are there shell holders that come in varying thickness that can solve the shoulders don't bump/die too long issue?

    (I just sand the top of my shell holder a bit with the sand paper on a very flat surface and that is usually enough to get the small bump I am looking for ...)
     
  7. jmden

    jmden Well-Known Member

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    Catshooter, Thanks for the reply. I'm not sure what to make of the situation, though, as after I annealed, the +.010 Redding Comp shellholder put 'em right where they should be when it or the +.008 wouldn't before. Didn't try 'multi-bumps'. I'll have to tuck that one away for later. ?? What do you think?
     
  8. CatShooter

    CatShooter Well-Known Member

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    Oh, you wascle... the secrets you keep.

    Lookie - the Redding +.010 comp shell holder make your headspace 0.010 LONGER than standard.

    If the cases don't want to go in the chamber (they are tight), then you want to pull the shoulder back a little, not move it forwards.


    If this happens again, use a (GOD FORBID) a regular shell holder, and it'll solve the problem faster... by using a "+" shell holder, you were making it more worser.

    In something like this, it is really the corner of the body/shoulder junction that resists changing - it's not "work hardened" but it is harder than the neck - if you soften it by annealing it, it will move easier... but a standard shell holder would also probably do it too.

    Over the years I have made up a bunch of shorter than normal shell holders to solve problems like this - I mark them with a red sharpie pen, and keep them in little baggies, separate from the others. Last month, I made a #10 shell holder that was 0.023" shorter than standard so I could resize 600 pcs of fired Lapua .223 brass that was given to me, that wouldn't go into a chamber that WOULD accept new factory brass, and I was using a small body FL die (go figure ??).

    .
    .
     
  9. jmden

    jmden Well-Known Member

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    I use the +.010 Redding Comp Shellholder because that bumps the shoulder back .002 from fireformed case headspace measurement in my rifle. I lapped the barrel/action junction and while the barrel was off, lapped the lugs with Brownell's tool and the combination of the two resulted in using the +.010 Redding Comp Shellholder to set back the shoulder .002. Thanks.
     
  10. Mikecr

    Mikecr Well-Known Member

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    Don't know what cartridge your using, or what affects sizing will have on POI.
    But for bolt closure/bumping you may need to trend your brass growth after sizing. After many reloads brass tends to springback -over days.
    With a couple of my cartridges I bump only .001 for shooting that day, .002 if it'll need to chamber well a week later. For season ammo made a month or more ahead, I bump .003.

    This growth may not occur for you, but it's a good idea to grab a round out of the box and check it with a gizzy before heading off to the range with a bunch. You may find it has grown a bit from previous measurements.
     
  11. goodgrouper

    goodgrouper Well-Known Member

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    I would have to agree with catwhacker here (on the subject at hand anyway). I don't think you have a work hardened neck, I think your dies aren't bumping your shoulders back enough.

    A work hardened neck would not prevent you from sliding a round into the chamber and not being able to close the bolt easily. That is a headspace problem that comes from dies that aren't doing what they are supposed to.

    I actually do the exact same thing as CS and have a set of shellholders cut off and seperated from the rest by a red marker on them. With that, you can actually make your FL sizing die a true FL die and not just another neck die.

    Or you can have your die cut off some but that will just fix that one problem. Since you are sure to run into this again if you buy any amount of dies, you just as well prepare for them all and have shellholders cut off instead.
     
  12. CatShooter

    CatShooter Well-Known Member

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    You still haven't said what case/cartridge this is...

    ... but it "sounds" like you have a chamber that is 10 thou too long for your bump die, so you are using a +10 shell holder to compensate... (are you using a real bump die, or just using a FL die?)

    If you use shorter shell holders, you can control the amount of bump - a +8 shell holder will make the case 2 thou shorter (in headspace, not OAL), and a +6 shell holder will make it 4 thou shorter.

    I am an "annealer" and do lots and lots of annealing, so I'm not knocking it, but in this situation, you might be better served by having a +8 and a +6 shell holder in your kit. Then you can "tweak" any tight cases without dragging out the ol' propane torch.

    GG...
    I'm not fussy, I take it where I can get it. ;) ;)

    .
     
  13. jmden

    jmden Well-Known Member

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    Interesting...I'll have to measure that with my 'gizzy'.
     
  14. jmden

    jmden Well-Known Member

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    CS, 300RUM shooting 240SMK's seating to the lands. Fourth or fifth firing when I started to notice this 'issue'. FL die which crushed 'em down and works 'em way too much. Adjust using the Redding Competition Shellholder kit that has 5 shellholders (+.002 through +.010 at .002 intervals). A +.010 shellholder does the minimum amount of sizing (in my rifle) while still allowing the case to chamber. My understanding of these mechanics are that using the +.010 shellholder (check out how Redding Comp. Shellholders work...?) increases my casehead to mid-shoulder dimension +.010 over what the standard shellholder and FL die would do. The Redding Comp. Shellholders are used to control 'bump' in my understanding. The cases would not bump before annealing (after several firings), now they do.