Nuther sizing die question from a noob......

Discussion in 'Handloading and Reloading' started by Howa 9700, May 31, 2021.

  1. Howa 9700

    Howa 9700 Member

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    Getting back up to speed after all these years, I'm beginning to understand why my Dad threw in the towel on loading for metalica and stuck with factory loads. Lots to learn and a lot of it confusing and contradictory. By comparison, reloading for shotguns was so easy even a child (me) could do it.

    So doing my research on reloading techniques, I find references to fine tuning the sizing process by use of case comparators, including several helpful Utubes showing how. All say the goal when setting up your sizing die is to set shoulder bump back anywhere from .001 for bolt guns (we are talking rifles here) to as much as .004 for semi-autos. Do that and you wring out good accuracy, not to mention extend case life. Or so the story goes. Sounds like good advice, so I decide to put it into practice.

    So yesterday, I'm setting up my sizing die for some .243.......carefully measure my case.....then follow directions for the dies.......which tends to go along the lines of...."raise ram on your press all the way, then screw in sizing die until it touches......lower ram and give it another 1/4 turn, then lock it down". I have 4 different brands of dies (Lee, RCBS, Hornady and Bonanza) and all pretty much say the same thing. Do that and your sizing die is set. No mention of getting that .001 shoulder bump.......but no worry, I can measure for that. So I do.......and what do I find? My shoulder bump is now EXTENDED by .001. Sizing the case does not decrease shoulder bump....it makes it longer?

    My first thought is I didn't set die low enough, but quickly realize that once a die is bottomed out, it can't go any lower.

    So what gives? Here is what I am thinking and if any of this is wrong, feel free to set me straight.

    First is it seems to me that dies are made to form brass back to SAMMI specs. Both as to diameter and length. How much a die will size any brass thus depends on how much the brass needs to be worked. If fired in a loose, sloppy chamber, it may need a lot. I'm reading where military rifles often have chambers to the large size so most ammo will chamber and fire. Custom and other precision rifles being the other end of the spectrum and may not allow the brass to move much at all.

    Second is it may take several firings before brass fully fire forms to a chamber. My assumption going in is would do that every time. That may be wrong, or it may be that the guns I'm loading for have tight chambers and are at min SAMMI specs and may not allow much case expansion? I know that for two of them, when I measure once fired brass in a Wilson case gauge, all brass still fits as to headspace and length. So basically, the brass I was sizing yesterday didn't need any shoulder bump. So how did it get longer? Only thing I can think of is the effort required to pull the neck sizer out was enough to also stretch the neck a bit with it. What I didn't do, but now realize I need to do is measure case length before and after sizing. Normally, I'd think of it as sizing forces the metal to go somewhere, but hadn't considered that the friction of pulling the neck sizer out would be enough to stretch the case with it.

    But as far as setting up the dies for shoulder bump is concerned, one of the ideas that makes the most sense to me when using a bolt gun, is to strip the bolt......and if a fired case will not chamber, keep adjusting the sizing die down until the bolt will just barely close on a sized case. The only way I can see that happening with a normal die is to NOT follow the directions.......in fact, do the opposite. Screw the die down until it touches, then back the die up a half turn. Then start an incremental trial and error process until the the bolt just barely closes. That may be far less sizing than what the die instructions call for.

    Or forget the technical stuff for now and just follow the directions to begin with? Where is the fun in that?
     
  2. Dale Alan

    Dale Alan member

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    Stripped bolt does not lie . I believe the die makers are depending on folks to have common sense when it comes to their lack of instructions .
     
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  3. Cemetery21

    Cemetery21 Member

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    ^^ agree. Instructions should work for someone sizing for "any/all" chambers. For those of us that want brass customized for one rifle/chamber, we need to find the die setting for the "bump" we prefer. Or for those wanting to custom bump for multiple rifles, set the die up for the shortest chamber in the mix.
    Otherwise, follow the maker's instructions. About the worst that could happen is maybe shorter brass life if you have a "generous" chamber.
     
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  4. Walkalong

    Walkalong Moderator Staff Member

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    How are you measuring shoulder position?

    Is the die touching the shell plate/holder when actually sizing a case?

    Yes, it takes more than one firing to fully form brass to the chamber, because it has to be able to extract easily, but too many people get hung up on this.

    Measure several fired cases to get an average shoulder position, then adjust the die to move the shoulder back .002 and you be fine. It will chamber fine, it will extract fine, and it will last many firing without developing any case head separation. Eventually the primer pockets will loosen up and you'll have to scrap it.

    There are plenty of ways to measure shoulder position before and after sizing. Some cheap, some not so much, they all work with care.
     

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  5. NMexJim

    NMexJim Member

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    You can use a neck sizing die for .243, but eventually, you're going to have to FL size. You'll start having chambering and bolt lift problems to the point you may have to smack a bolt open. I could get maybe 3 or 4 neck- size-only reloadings on a case before FL, but that wasn't guaranteed.

    I quit neck sizing after some of these issues. Here's an article that might help. He starts with screwing the die inward, so read carefully.

    TECH Tip: How to Set Your Dies for Correct Shoulder Bump « Daily Bulletin (accurateshooter.com)

    If you look at the bottom of that page, there are a couple more articles you might find of interest.

    BTY, I use .002 bump for my .243 and problems went bye-bye except for annealing. .243 will work harden pretty quickly depending on how hot the load is. I anneal after 4 firings.
     
  6. Charlie98

    Charlie98 Member

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    That....^^^ Resizing .348WCF brass, which is quite heavy, gave me fits for a while... until I realized setting the die, and then checking the die when the ram is up with a case were two different things. There is enough tolerance slop in most presses to make this a factor.

    Set your die according to the instructions... then set a case and run it up into the die. With the ram at full upward position... check the clearance between the shellholder and the bottom of the die... I'll bet there is a gap. Withdraw the case enough that you can adjust the die down further... ram it up and check it, again.
     
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  7. AJC1

    AJC1 Member

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    I'm just going to keep it real simple. Size a case and see if it chambers. I'll bet your still below sammi spec. The hornaday tool is helpful for more advanced techniques and your trying to run the Olympics before the state championships.
     
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  8. Blue68f100

    Blue68f100 Member

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    What you see is the results of the body being sized make the brass grow. Once you over come this you start moving the shoulder back. So you just stopped too early. If you had continued you would have seen the shoulder move back.
     
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  9. Howa 9700

    Howa 9700 Member

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    Attempting to measure bump using a Hornady case comparator.......mounted to my dial calipers. Measuring before sizing, and after. When I was trying this yesterday, I did not have a printout of the SAMMI specs for the 243 win, which is the only place I know of to find the published number for what the length to shoulder should be. If a new or once fired case is at or less than this number, I would not expect a full length die to have any influence on it........in other words, will give it "no bump" cause it doesn't need any. Which means it could be I was looking for something that wasn't there.

    But it was about that time when I recalled someone on THR mentioned to me once that if a guy wanted custom dies made for a specific rifle, die maker would want 3X fired brass to assure it had fire formed to that chamber. It was about then the light came on.

    Guess my point for even bringing it up is the fact that someone like me discovered the issue of shoulder bump, and attempted to do it, not knowing a whole lot of stuff needed to be known and understood in the middle. There is a pretty big gap or step between what the die maker's instructions are and what some folks are actually doing.

    And yes I went from grade school level to grad school level and managed to skip past all that in the middle.

    At this point, I have a pretty good start on what could be an entire chapter about dies for a reloading manual. The one I'm thinking of is my Lyman 50th. They left out a whole lot of good stuff that folks on this forum talk about daily.
     
  10. Howa 9700

    Howa 9700 Member

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    That was my first thought. If I keep lowering the die, I'll get some bump eventually. After one full turn.....I realized that once the die bottomed out on the ram, it would go no further. Ram simply stopped before handle could bottom out and raise ram any more. It only goes so far. There may be dies that do, but these were Lee dies, and once they bottom out, they will go no further. But the same appears to be the case with the RCBS and Hornady dies. They all only go so far.

    It was about then I concluded that must be the situation with once fired brass that had not yet stretched to the point the die made any difference to it.
     
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  11. Walkalong

    Walkalong Moderator Staff Member

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    Amen brother, amen. :)
     
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  12. Walkalong

    Walkalong Moderator Staff Member

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    Possible, but it is the rare die that won't move the shoulder of fired cases, look at everything else carefully before assuming a die issue.
     
  13. 243winxb

    243winxb Member

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    Is to compare sized brass to the fired brass from your rifle. Nothing else. Forget SAAMI.
     
  14. NMexJim

    NMexJim Member

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    In past threads, there have been many discussions on the relative merits of various die makers. Some liked one or the other, but I’ve not heard of anyone encountering a mis-cut die. I’m sure it’s happened, but it’s very rare.

    Let’s try some videos. Go to YouTube, Sinclair home, and under Case Sizing you should find 3-parts.
    1. Why We Full Length Resize
    2. Setting Up A Die
    3. Using A Bump Gauge (AKA: headspacing comparator)
    As 243 says, forget about SAAMI for the time being and just use the tool to measure your fired cartridges to each other and the progress of your sizing. However, I’ll attach .243 standards and encourage you to read the allowed tolerances. I think the reason to set SAAMI aside is that it’s nearly impossible to manufacture a comparator set to headspace tolerances. That measurement is on the shoulder angle which really complicates matters.

    If you’re bottoming the die on your ram, them you’re getting all the sizing you can. If you’re not getting any shoulder bump, then your cases are not fully expanded and may need another firing or two.
     

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  15. Blue68f100

    Blue68f100 Member

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    Check to see it it's touching the shell holder when your sizing with the ram fully up. Presses have flex and this must be adj out. If you have a gap between the shell holder and die with it fully up and under load, you need to turn the die down a little more, and try again. A presses have flex, some just have more than others.
     
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  16. NMexJim

    NMexJim Member

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    In addition to what Blue says, “cam-ing over” is when the die is more than against the ram - zero gap plus some interference fit. The press handle will stop and then, with a little more pressure, will “pop” over. I personally do not use a lot of cam over; maybe just a tiny amount to make sure slack is out.

    When your cases are fire formed enough, then you’ll have to back to die out to keep shoulder bump from being too much. My method is to back out the FL die several turns, put in a fired case and raise the ram, screw the FL in until it just touches, and start from there. Continue turning the die inward in small Increments until you have about .002 shoulder setback.
     
  17. Howa 9700

    Howa 9700 Member

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    Have checked and verified that these once fired cases are fully bottomed out in dies. That, plus when I measure for case length, they are well below any need to trim, so beginning to suspect they simply have not yet stretched to the point where the dies are having any affect on shoulder bump.

    Good learning experience however. Have a much better understanding of what the consequences are of following the die maker's instructions, vs. what folks are doing to get a custom fit of resized case to an individual gun.

    BTW, checked my Lyman 50th again and there is a reference to all this in a topic called "Advanced Case Prep". Problem being I doubt an uninformed reader is going to gain anything from it. There is no background theory to get the reader up to speed, so the references to shoulder bump would only be understood by someone who already knew as much about it as the author did. Probably would have made for a good magazine article, but out of place in a reference manual. Missed opportunity.
     
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  18. edwardware

    edwardware Member

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    You can't compare to the SAAMI drawing. The comparator does not necessarily rest on the case at the datum diameter, and the measurement is very sensitive to diameter.

    And, you don't need to. Measure your fired brass, move the shoulder -0.002", and carry on.
     
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  19. FROGO207

    FROGO207 Member

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    In the past I have purchased spare shell holders and ground some off the top to get my prefered sizing. There is also a set you can buy available, I think from RCBS. Just make sure that you need to size shorter first though.
     
  20. Walkalong

    Walkalong Moderator Staff Member

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    Yep. Although I modded my die.
     
  21. 243winxb

    243winxb Member

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    Finding the true chamber size, head to datum of fired brass.

    I put some Break Free CLP on the body of 1 round of factory Hornady 6.5 CM 140 gr ammo today. This produced harder then normal bolt lift. It also produce the longest head to datum measurement i have recorded, by .002"
    Putting the fired case back into the chamber, produced a slight crush fit on bolt closing.

    Not recomended to do, as bolt thrust/breech pressure would be high.

    Online, wildcat cartridges are said to fire form better with some light* oil? Keeps the brass from sticking to the chamber and causing excessive stretching, helps avoid case head separations.
     
    Last edited: Jun 2, 2021
  22. AJC1

    AJC1 Member

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    If your just dying to measure and check the rcbs tool will measure exactly and give you.plus minus sammi spec. They are expensive but are a quality tool.
     
  23. South Prairie Jim

    South Prairie Jim Member

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    I would echo this as well, seems a lot of fellas try to bump a shoulder before its fully grown .
     
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  24. brickeyee

    brickeyee Member

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    Get a 'body die.'
    They are set up to size the case body without affecting the neck.
     
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