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Thread: Cores popping loose

  1. #1
    Boolit Buddy
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    Cores popping loose

    I am sure that I am doing something wrong. I am seating cores in 6mm rebates boat tail dies and on the upstroke the cores are jumping up in the jacket. Sometimes the core comes all the way to the top of the jacket. Seems to happen more often with soft lead versus a small amount of alloy.

    Cores are cleaned with brake cleaner and the Coleman fuel before drying for at least a day.

    Any thoughts are welcome. Thanks.

  2. #2
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    Winger Ed.'s Avatar
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    Is there a mark where it looks like the soft Lead is getting enough of a grip on the die to pull on it?
    If so, I'd just switch over to a harder alloy that doesn't do that.

    In these depressed economic times, you might want to switch away from Coleman fuel.
    It's just the cheapest of old school no-Lead gas that in the old days was called white gas.
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  3. #3
    Boolit Buddy
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    Could it be cores are too large for jacket? I never had that problem personally, but it sounds like air may be getting trapped under the core while trying to seat, especially if a tapered wall jacket is being used. Just a thought...

  4. #4
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    Checked that, there is 0.022" clearance all the way around. I have found that if I back off some and don't make the base as filled out the problem seems to go away. Don't get a squared base that way though.

  5. #5
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    The way the big boys, as in the major companies, do it, is to make the core the same shape as the jacket. If the bullet is a boat tail, then the core is also a boat tail to fit the contour of the jacket prior to final swaging.

    I've toured the Sierra and Nosler factories and that's how their boat tail bullets are made. I still have samples of each step from the Sierra factory around here somewhere......

    Hope this helps.

    Fred
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  6. #6
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    You are not fully seating the cores. Measure the jacket diameter before core seating and after. The jacket should be .001 to .002 larger after seating the core, depending on how the dies were made. This jacket expansion and the jacket “springiness” is what locks the core in the jacket. Each die in the set is designed expand the jacket by at least a small amount.

    The other possible option is that your core seating punch isn’t the correct diameter, preventing the core from seating properly and expanding the jacket. The correct punch diameter depends on the jacket thickness and how deeply the core is seated, since the jacket is tapered on the inside. Different core weights will take different punches since the top of the core ends up at a different distance from the jacket mouth. If the punch is correct, the seated core will be flat on the top with no lead flashing that gets past the end of the punch. The brass will also not have a bulge from the seating punch.

    You do need to make depth adjustments slowly though since there is a LOT of pressure seating cores and you can bend punches.
    Last edited by garandsrus; 07-09-2022 at 12:04 AM.

  7. #7
    Boolit Buddy
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    I have to agree with garandsrus that he has identified the major issue why the cores are loose in the jackets. Using hydraulics I never had an issue. It takes quite a bit of pressure to fully seat the core and expand the jacket to the diameter of the die being used. Core seating is the most important operation because it determines what the final bullet diameter will be. All remaining operations will not change the final bullet diameter.

    Punches do need to match the ID of the jacket, so you don't get any lead bleeding past the punch. I use mostly annealed cases for jackets, and it does take a lot of pressure to fully expand the case. I could never see doing them on a reloading press without hearing something break. I never bent a punch from over pressure. I've bent one or two when a case tipped doing core seating and didn't stop the ram soon enough. That's where hydraulics are unforgiving. My cycle times are are seven seconds or less and you have to pay attention.

    If done correctly the jacket needs to fully expand to the die diameter. If you successfully do that, I can't see a core being loose. I've already used 44/cal copper jackets to make 45/ACP bullets. With the correct die setup, the jacket fully expands and the core fully seats perfectly.

    There is a lot involved in swaging and it's taken me years to figure most of it out and I'm still learning.

  8. #8
    Boolit Buddy
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    The diameter of the jacket after seating is 0.2433. If I bump the pressure up the jackets pop at the lead line. I don't think I have any more room there.

  9. #9
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    Is there lube inside your jackets? Maybe try solvent cleaning a few jackets to see if it goes away. The only times I have had cores pop is when there was lube contamination somewhere. Cleaning a few jackets is a simple thing to try to solve the problem or eliminate another variable. Good Luck!

  10. #10
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    I clean my jackets (made from 22LR/17HMR/22WMR or 5/16 copper tubing) using dawn liquid soap and a Harbor Freight ultarsonic cleaner.

    Attachment 301938

    I tend to believe that either the Core Swage die or the punch are the incorrect diameters.
    Mustang

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  11. #11
    Boolit Buddy
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    I have an ultrasonic that I can run the jackets through. If I use a punch that is too small and bleeds by they don't come loose. ��

  12. #12
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    Quote Originally Posted by silverjay View Post
    The diameter of the jacket after seating is 0.2433. If I bump the pressure up the jackets pop at the lead line. I don't think I have any more room there.
    The jackets are coming loose and the jacket is .2433? That doesn’t make any sense at all. Based on saying that an increase of pressure will “trim” jackets, you may be significantly over pressure when seating. Use the same punch and back doen on the pressure.

  13. #13
    Boolit Buddy
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    Looks like it was too much pressure and the taper of the boat tail was pushing the core out.

  14. #14
    Boolit Master Sasquatch-1's Avatar
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    I would try seating the core slower and leaving the punch down for a 5 or six count to allow any air trapped underneath to escape. I don't know if this will solve your problem, but it's worth a try. Also, is there any space between the core and the jacket when you first insert the core? You may not have enough space to bleed off trapped air.
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  15. #15
    Boolit Buddy
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    There is ~0.020" radial clearance. I have been letting them sit for a five count at the bottom of the press stroke.

  16. #16
    Boolit Buddy Alex_4x4's Avatar
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    Quote Originally Posted by garandsrus View Post
    ...

    The other possible option is that your core seating punch isn’t the correct diameter, preventing the core from seating properly and expanding the jacket. The correct punch diameter depends on the jacket thickness and how deeply the core is seated, since the jacket is tapered on the inside. Different core weights will take different punches since the top of the core ends up at a different distance from the jacket mouth. If the punch is correct, the seated core will be flat on the top with no lead flashing that gets past the end of the punch. The brass will also not have a bulge from the seating punch.

    ...
    Exactly.

    And it should be remembered that J4 from different manufacturers may require different diameter top punches.
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  17. #17
    Boolit Master


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    I was told that some of the benchrest shooters that I knew would wash the cores in dishwashing soap and it would cause the cores and jackets to bond together.
    I have never tried it.

  18. #18
    Boolit Buddy
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    These are Sierra jackets. When I backed off on seating pressure, problem went away.

  19. #19
    Boolit Buddy
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    May try the dishwasher soap, can't hurt.

  20. #20
    Boolit Master

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    What lube are you using when you squirt the cores ?

    Bill
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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check