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Thread: Neck tension

  1. #1
    Boolit Buddy
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    Neck tension

    After resizing, I found some cases hold the bullet nice and firmly while others let the bullet fall into the case. All were manufactured by the same manufacturer, appeared once fired and identical in dimensions. This occurs with or without the expander being utilized. The cartridges are being used in a single shot, and as I don't have a crimp die, I do not have the ability to crimp. Couldn't anyway, as the bullet falls into the case. Why does this happen? Would annealing the necks prior to sizing correct the problem, or make it worse? The cartridge is an improved 25-20 Winchester. As dies are not available, I've been using a Herter's Universal neck sizing die which works well on most cases while others don't resize adequately. I have a very limited supply of 25-20 cases so I'm hesitant to try anything which will ruin the brass I have. Thanks, Dan

  2. #2
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    Winger Ed.'s Avatar
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    Annealing can't hurt the brass, but I'm not sure that would correct your issue either.
    If some cases are tight, and some not- that sounds like a difference in wall thickness at the neck.

    I'd encourage getting a new, and full set of dies.
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  3. #3
    Boolit Master

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    I think your brass is just too thin for the intended bullet. But I think it is odd that original and final bullets size are the same. Am I correct in this assumption? I have found this when making 38-55 from 30-30 for example, or some 11mm from 348 or 8mm Lebel. Are you sure you get a undersized bullet? In my example I found no cure, maybe paper patch or powder coating. but that really does not solve the problem. Hopefully some one else has some knowledge. good luck

  4. #4
    Boolit Master Hannibal's Avatar
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    Check the diameter of your bullets and the interior diameter of your case necks of several different ones, say a dozen of each and write down your findings. You'll find that one or the other isn't consistent and maybe both.
    Depending on which one is inconsistent will determine the action you need to take. You'll need a 1" micrometer and pin gauges would be ideal for the case necks, but you might get by with an accurate caliper but just realize that it might be pretty difficult to get a repeatable, accurate measurement.
    You'll want the case neck ID to be about .002" smaller than the bullet ID. Crimping wouldn't fix the issue and would cause accuracy problems if you're trying to use a crimp to correct a neck tension problem. The bullet should be held in the case neck by neck tension as explained above, not a crimp made by the seating die. As others have said neck wall thickness could be inconsistent especially if this is a hodgepodge of mixed brass but the expander/ mandrel in the sizing die should make the ID consistent under normal circumstances.

    If the bullets are the culprit then you'll need to take a look at your alloy and casting/mold temperature. If it's the case necks I'd try annealing the necks and if that doesn't work then something is amiss with either your sizing die or your technique such as lube, force applied to the press handle, ect.

    Also, if you aren't already doing so deburr your case necks both inside and outside after sizing. It doesn't take much to scuff up the outside of your bullets and this will be detrimental to accuracy.
    Last edited by Hannibal; 06-25-2022 at 12:30 PM.

  5. #5
    Boolit Buddy
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    Thanks for all the replies. My bullets are swaged copper tubing bullets, right on .257" and consistent. A bullet held tightly in one case will drop thru another. I was thinking maybe some cases have more "spring back" than others, and in this were the case, annealing could help. The cases are W-W and never experiencing this in the past I thought it a good topic for discussion. I have telescoping gauges so I'll attempt to get an inside measurement on a few cases, though it is very difficult to get accurate readings on a very short case neck.

  6. #6
    Boolit Master Hannibal's Avatar
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    Quote Originally Posted by Danth View Post
    Thanks for all the replies. My bullets are swaged copper tubing bullets, right on .257" and consistent. A bullet held tightly in one case will drop thru another. I was thinking maybe some cases have more "spring back" than others, and in this were the case, annealing could help. The cases are W-W and never experiencing this in the past I thought it a good topic for discussion. I have telescoping gauges so I'll attempt to get an inside measurement on a few cases, though it is very difficult to get accurate readings on a very short case neck.
    Measurements will indeed be tricky and require patience but are a necessity to know for certain the cause of the problem. If you are certain that your bullets maintain consistent diameter then the problem has to lie within case neck diameter so the question is why aren't they consistent. This is where measurements are necessary so you can experiment and nail down the source.

  7. #7
    Boolit Master hoodat's Avatar
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    You said the brass is all WW, but do you know the history of them? Did you purchase them new or as ammo? 25-20 is a case that is notorious as being reformed from Bee or 32-20. Is it possible that someone turned the necks at some time?

    I've got brass that I purchased used at the gun show, that has thinner necks than my standard batch. I save those for cast bullet reloads where my diameter is .001 or more over bore.

    You could spring for a bushing die, and size those to a workable diameter. jd
    It seems that people who do almost nothing, often complain loudly when it's time to do it.

  8. #8
    Boolit Master

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    back again- I fought this one a few years ago with a stock 38-55. I am not sure what a modified 25-20 is - has been modified from what to what. Any chamber cutting involved? It sounds like you might need to get a tight neck sizer and re-expand to suit. Then neck turn to suit. I prefer turning to reaming because in the '60 -'70's when I was learning it was considered better than reaming. Maybe somebody will weigh in with a more current enlightened opinion/info.
    Annealing won't help as the brass will stretch a bit more on firing, meaning bigger hole in fired case. If your tight cases are the "hard" ones, ( more spring back) then annealing will probably make them all loose.
    I think you could make a usable plug gauge fron a bullet you now have. Take a .257 bullet, seat in case backwards. You now have a poor mans plug gauge that's dead on. Go through and sort by "wont go", loose and sloppy" and "snug". Use the "won't go" and snugs". You might try this before neck sizing and then again after.
    You might try a measurement of the chamber in the neck area. Or, how big a bullet can be seated with no neck sizing? Is .257 perfect for the bore? Maybe going to .258 or ,259 will work out better in the long run.
    good luck

  9. #9
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    If you don't know the brass history or if they're from the same lot, maybe try some new unfired cases.
    If they were mine I'd anneal and resize, if that didn't help at least it would eliminate one possible cause.
    The neck ID would be measured best with a gage pin. If I was to go that route and didn't have a set of them, I'd buy at least a .255" and use that as a go-no gage. It won't fix your brass but you'll be able to identify the loose necks.
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