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Thread: Different results seating GCs

  1. #1
    Boolit Master

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    Different results seating GCs

    So if I seat the check via a top punch (inverted) checks seat fine but I just noticed a slight dome it was creating. Right side up naturally check is more concave. Would this really affect blow by?


    Left is check going in first, right is pill going first.


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  2. #2
    Boolit Master uscra112's Avatar
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    Your top punch keeps the bullet aligned with the die. Doing it inverted won't do anything good for the overall straightness of the bullet nor the squareness of the seated check.

    Do it the way the sizer was designed to work.
    Eleutheromaniac

  3. #3
    Boolit Master

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    Quote Originally Posted by uscra112 View Post
    Your top punch keeps the bullet aligned with the die. Doing it inverted won't do anything good for the overall straightness of the bullet nor the squareness of the seated check.

    Do it the way the sizer was designed to work.
    I have an NOE sizing kit (.265) and they included a top punch holder specifically to size bullets base first. This is supposed to crimp the check a little better to bullet. My question was about it creating a slight dome at the base of check.


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  4. #4
    Boolit Master uscra112's Avatar
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    If the GC is seated square, I don't think the dome will make any difference.

    The old Ideal handbooks told you to use a flat-face bottom punch for plain lead, a slightly concave one for gas checks. Purpose being to keep lube from getting between the bottom punch and the bullet. Lyman dies at least come with a concave bottom punch. The other end is flat, though. Try flipping yours over to see what happens. The chamfer won't be any problem since you're sizing a powder-coated bullet.
    Eleutheromaniac

  5. #5
    Boolit Master

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    Quote Originally Posted by uscra112 View Post
    If the GC is seated square, I don't think the dome will make any difference.

    The old Ideal handbooks told you to use a flat-face bottom punch for plain lead, a slightly concave one for gas checks. Purpose being to keep lube from getting between the bottom punch and the bullet. Lyman dies at least come with a concave bottom punch. The other end is flat, though. Try flipping yours over to see what happens. The chamfer won't be any problem since you're sizing a powder-coated bullet.
    Will do. I usually pre-seat all checks by using the flat side of the nose sizer and the push rod. This is the only way I can get them square.


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  6. #6
    Boolit Master uscra112's Avatar
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    I've never powder-coated a bullet. (only motorcycle frames). Is there plastic on the base that might interfere with getting the GC seated square?
    Eleutheromaniac

  7. #7
    Boolit Master

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    Quote Originally Posted by uscra112 View Post
    I've never powder-coated a bullet. (only motorcycle frames). Is there plastic on the base that might interfere with getting the GC seated square?
    No but there's a minute pesky miniscule ridge around the base that I have to ever so slightly chamfer to get the check on without shaving off lead. I always cull my bullets making sure each and every one was evenly cut with sprue. I'm beginning to think that when the manufacture the checks, the walls are not straight but rather turn inwards ever so slightly.
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  8. #8
    Boolit Master uscra112's Avatar
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    I you're using Hornady checks, you're right, sorta-kinda. They have a slight burr at the mouth of the cup that helps them grip tighter. The checks that Sage's sell do not have this, and I have had them pull loose as I remove the bullet from the lubrisizer.
    Eleutheromaniac

  9. #9
    Boolit Buddy dimaprok's Avatar
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    Depends on bullet design and gas check. I found that with some bullets like RCBS and Lee (30 cal) and my homemade GCs Lubrisizer does a better job of seating (grip better) and no need to pre-seat them. With NOE I get perfect results with Lee push trough die, bases are square and never concave. If you powder coat first than yes you need to seat them first to make sure they'll seat even and square. If you have NOE punch shell holder, you can get a piece of 7/8 - 14 rod or bolt with flat face and screw that at the top with ram extended all the way up you screw it in until it touches the bullet top and than just a little more that way you have always consistent seating for all your gas checks. Be careful though because if you screw in too much you can end up with bullets becoming "thick" and ending up being .312+ in diameter which might or might not be desired effect.
    PS. I made my own bullet holder out of delrin, its very simple.

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  10. #10
    Boolit Master

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    I wish they made molds where you could pre-install checks and then pour "nose first". Of course this would only work with FN bullets.
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  11. #11
    Boolit Master
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    I'll get a slight dome on bullets from specific molds and not on others. An example would be, never on my MP 314-640 115gr and always on my MP 314 Sledgehammer. My Sledgehammer has a fat GC shank that won't allow a GC on without using a NOE edpander, and the -640 will allow the GC to click on. Both of these bullet molds drop very accurate bullets. I don't see the slight dome as a detriment to accuracy as it's consistent as the sunrise. All of my bullets are PC'd and sized with Lee dies.

  12. #12
    Boolit Master

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    I'm gonna leave em as is. If a boat tail can go sailing straight then these will. Never could quite figure out that analogy with boat tails and bullet getting a seal without gas cutting.
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  13. #13
    Boolit Grand Master Bazoo's Avatar
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    I would think that they would seal better. Pressure would be against the dome pushing it so it would be trying to flatten, causing the sides to push against the bore more tightly as pressure increased.

    I’ve never shot any like this, but we are about to, out of my buddies Winchester 94 in 32ws. The die I have had a concave I piece and the gas checks are a bit larger in diameter than ideal. The results are perfectly convex bullet bases.

  14. #14
    Boolit Master uscra112's Avatar
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    The only thing that matters is whether the check is exactly square to the axis of the bore as it emerges from the muzzle. If so, the escaping gas acts uniformly all round. If not it gives the base a little sideways kick. The bullet departs with some yaw. and in air it flies a spiral path. which may or may not coincide with the point of aim when it gets to the target. A bad crown does the same thing, which is why the crown is so important.
    Eleutheromaniac

  15. #15
    Boolit Master

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    Last 2 posts make a lot of sense. I kinda had that in the back of my mind but I'm no physics major.
    The unexamined life is not worth living....Socrates
    Pain, is just weakness leaving the body....USMC
    Fast is fine, but accuracy is FINAL!....Wyatt Earp

  16. #16
    Quote Originally Posted by uscra112 View Post
    The only thing that matters is whether the check is exactly square to the axis of the bore as it emerges from the muzzle. If so, the escaping gas acts uniformly all round. If not it gives the base a little sideways kick. The bullet departs with some yaw. and in air it flies a spiral path. which may or may not coincide with the point of aim when it gets to the target. A bad crown does the same thing, which is why the crown is so important.
    This is paramount to accuracy. The base must be perfectly square and flat. Any convex or concave would have to be the exact same for each bullet, which is a whole separate issue. Dead flat and square works.

  17. #17
    Boolit Buddy dimaprok's Avatar
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    Quote Originally Posted by B R Shooter View Post
    This is paramount to accuracy. The base must be perfectly square and flat. Any convex or concave would have to be the exact same for each bullet, which is a whole separate issue. Dead flat and square works.
    I've heard this repeated many times until I slugged the bore and noted how initially flat base comes out deformed from the rifling cut in to it! There are ridges formed. Too bad I don't have a picture handy, so much for perfectly square base nonsense! In reality its very different!

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  18. #18
    Boolit Master uscra112's Avatar
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    Squareness of the base and the furrows cut by the rifling are two entirely different matters, although the furrows must all be uniform or you'll get the same results as an out-of-square base. The matter of base squareness was proven conclusively over 100 years ago by Dr. Franklin W. Mann, with assistance from such geniuses as Harry Pope. Over the unsung generations it's been confirmed time and again by later experimenters.
    Eleutheromaniac

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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