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Thread: Effects of off-center sprue in rifle bullets?

  1. #1
    Boolit Master
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    Effects of off-center sprue in rifle bullets?

    I bought this mold off of ebay. These older Ideal 266469 are hard to come by as they drop a .268" bullet. I took the chance with this one. It was in very nice, excellent condition. It in fact drops .268" bullets. I have a current mold of this number and they drop .266".

    But when I used it the first time....ugh.... one of the sprues was way off to the side. I'm convinced the sprue plate on this mold is not original to the blocks. So as it is I can use it as a single cavity mold or go to the considerable trouble in making a new sprue plate on the milling machine (which I have).

    I bought from NOE their push-through sizer for .268" figuring I'd pan lube these for my various Swedish Mausers. I ended up using LLA but still have to attach and crimp the gas checks. I'm sure I used too much LLA but figured in a 29" barrel more was better.

    Any practical experience in shooting off-center sprue cast bullets?




  2. #2
    Boolit Master
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    If you have an accurate bore not much up to 100 yards
    " Associate with men of good quality, if you esteem your own reputation: for it is better to be alone than in bad company. " George Washington

  3. #3
    Boolit Buddy
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    I haven’t shot bullets with off center sprues. But I have shot some 30-06 Lyman 311291 bullets that the base was rounded and not perfectly square. After the gas check was installed I did not see a difference when shooting groups.

    I think that you should segregate a batch and see if the shoot differently.

    JM

  4. #4
    Boolit Master
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    Always remember what rifling is supposed to do! Even out irregularities! ( to a point)
    " Associate with men of good quality, if you esteem your own reputation: for it is better to be alone than in bad company. " George Washington

  5. #5
    Boolit Master

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    Shoot some and let us know. My hunch is it won't matter.

  6. #6
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    I think as long as the gas checks seat flush and squarely you'll probably be OK. I also agree with keeping them separated and test them at first, just to be sure. If I had the capabilities I'd make a new plate, IF your rifles like the boolits!

  7. #7
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    I don’t remember the issue number, but a Handloader magazine from years ago had an article about a guy that intentionally doesn’t completely close the sprue plate. He wants a smaller sprue that is off centered. It seemed to work for him so I would give them a try.

  8. #8
    Boolit Bub
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    It may not make a bit of difference, but if I had the equipment to make a new plate and the knowledge to use it, I would remove the doubt.

  9. #9
    Boolit Master
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    Unless the rifle is a genuine bug-shooter, you won’t notice a difference. I have a 311-316 that had the stop pin slightly misplaced, so that the sprue cut-offs were unequally off-center. Never made a difference that I could discern when fired from an iron-sighted Browning M-53.
    What I would do, just to put my mind at rest, is to cast up a hundred boolits, carefully segregating them, then load 25 centered cut off ones, another 25 with the off-centered ones, and then 25 with no regard as to which was used. I’d fire five, five shot groups with each load and compare the results. My bet is that you will find no significant difference.
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  10. #10
    Boolit Master uscra112's Avatar
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    Col. Harrison did an article about this about 50 years ago. Turns out that there's no discernable effect unless there's a void under the sprue.
    flectere si nequeo superos, acheronta movebo

  11. #11
    Boolit Master
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    I haven't seen it to matter when I had that to deal with.

  12. #12
    Boolit Master
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    You can always orient them in your loading and see if there is a difference.

    A few groups should show a pattern if so.

  13. #13
    Boolit Master redhawk0's Avatar
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    I've shot some off center sprue boolits. I've never seen any difference. A full cavity is a full cavity. Where the sprue is located is of no consequence.

    redhawk

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  14. #14
    Boolit Master


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    if you have a gun/load that shoots 3 MOA the effect may be masked...I do not know for sure. If you have a 1 MOA gun/load, it may matter...I do not know.

    I support the idea of testing as suggested above and then factoring in your expectations. In my ignorance, I would not purchase a mold that produced bullets like that...but I am ignorant.

    It would be informative if those who state "it does not matter", could supply more information. Were reports based on a small bullet or a large bullet? 1200 fps or 2000 fps? With GC or without? Slow twist or rapid twist barrel? My red flag goes up with "blanket" statements.
    Don Verna

    NRA Endowment Member

  15. #15
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    I believe if there is a void it will probably be under the sprue. I think it would depend on your ability as a caster. I would segregate the first 100 I cast and see what the groups are like.
    [The Montana Gianni] Front sight and squeeze

  16. #16
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    I have a 22 hornet that shoots the casties real well. At one time I got obsessed with getting 10 shots in an inch at 100 yards. One of the things I tried was the "not quite closed" sprue plate to minimize the sprue cut-off size (relatively large in a .225 diameter boolit). I tried several different amounts of offset: it made zero difference and I never did quite get 10 in that inch, but came close. I would not worry one little bit about that offset sprue cut-off.

  17. #17
    Boolit Grand Master

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    If , when cast , the base is smooth , flat and level ... the way a proper base should be ... the offset
    hole should make no difference ... in theory .
    I honestly believe once a gas check is installed they will all group the same .

    If not....built in alibi !

    Gary
    Certified Cajun
    Proud Member of The Basket of Deplorables

  18. #18
    Boolit Master
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    Lyman made two different sprue plates. About, I'm guessing, 12 years ago there was a lot of discussion here about it and also the Lyman part numbers. I actually ordered and received one but I had a heck of a time because it was not a current number in their system.

  19. #19
    Boolit Master
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    I would think not enough to notice. On the other hand, I am sure it will bother you much like it would myself until a new plate is made. Is the other mold a 2 cavity?

  20. #20
    Boolit Master
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    Could you have a out of spec sprue plate, or did the previous owner swap it out for another? If you have other Lyman 2 cavity molds, compare the sprue plates. If all else fails, contact Lyman, and see if a different sprue plate was used on older molds, and try to get one, or even make a replacement yourself. If the bullets shoot OK, and it doesn't bother you, leave it as is.

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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