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Thread: concentricity on cast

  1. #1
    Boolit Buddy leadhead 500's Avatar
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    concentricity on cast

    Has anyone tried using a concentricity tool to correct cast rifle bullets? If so what have the results been after correcting it?

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    Boolit Grand Master


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    Damage to the bullet resulting in less accuracy.

    Such tools depend on bending the case neck to "straighten" the bullet into better concentricity with the cartridge center line. A cast bullet is softer, even when HT'd of PC'd than the brass neck so it gives first.

    Much better method of obtaining better concentricity is to turn or ream the case necks to a uniform thickness and use sizing dies that maintain the concentricity better.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
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    My barrel make the bullets round.
    The solid soft lead bullet is undoubtably the best and most satisfactory expanding bullet that has ever been designed. It invariably mushrooms perfectly, and never breaks up. With the metal base that is essential for velocities of 2000 f.s. and upwards to protect the naked base, these metal-based soft lead bullets are splendid.
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    Forget everything you know about loading jacketed bullets. This is a whole new ball game!


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    Boolit Master Digger's Avatar
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    Quote Originally Posted by waksupi View Post
    My barrel make the bullets round.
    There ya go ....
    It is much easier to fool people ,
    than to convince them they have been fooled !

    If you can read this , thank a teacher ...
    If you can read this in English , .. thank a Vet !

  5. #5
    Boolit Master Traffer's Avatar
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    Barrels will "swage" the bearing surface of the bullet to the proper dimension. That's why everyone says a little bigger diameter is better.
    But a lopsided ogive can cause problems. AND a non uniform base (from what I read) will make even more problems for you. That is why I am making fully swaged-after powder coated bullets. I am hoping that it will help with consistency.

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    Boolit Grand Master

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    I believed the fellers above are correct; the barrel will swage/size the lead bullets. But what if the bullet starts out crooked? If the bullet is not concentric with the case and enters the barrel crooked, off center, what happens to accuracy then? I don't think the "proper dimensions" is all that matters with this subject as an uneven sized bullet, even if the same diameter may be "off balance?
    My Anchor is holding fast!

  7. #7
    Boolit Buddy leadhead 500's Avatar
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    I agree a 110% with the guys above about trying to correct it. I am curious about using the tool to sort out the loaded rounds to see if it would make any difference in accuracy, such as keeping them in a tolerance of 0.5 or less

  8. #8
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    The press and loading dies also have a lot to do with this.

    IF you don't load it perfectly straight --- you can't change it.

    RCBS rock chucker won the "shootout" of most concentric loading single-stage press done by gavintube

    https://www.youtube.com/watch?v=TqcYI0G2hqM

  9. #9
    Boolit Grand Master


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    Quote Originally Posted by mdi View Post
    I believed the fellers above are correct; the barrel will swage/size the lead bullets. But what if the bullet starts out crooked? If the bullet is not concentric with the case and enters the barrel crooked, off center, what happens to accuracy then? I don't think the "proper dimensions" is all that matters with this subject as an uneven sized bullet, even if the same diameter may be "off balance?
    mdi's questions are the crux of the matter. There are numerous tools made that measure the concentricity of the loaded round. I use the Hornady gauge and a custom made one by a bench rest/machinist friend. Both work very well.

    As I recall there is/was an excellent article in the NRA Cast Bullet Supplement dealing with "Crooked Necks" that also explains and offered a simple solution to the problem. As I previously mentioned, better these days [if there is a problem and your rifle and shooting skill can tell the difference] to turn the necks concentric and then use dies that will keep the neck concentric.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  10. #10
    Boolit Grand Master

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    Concerning "run out". I never checked run out on any cast bullet rifle handloads and my marksmanship would probably not be good enough to notice any difference. I didn't really give it a lot of thought until I saw some questions on a forum. I got a Hornady concentricity gauge. I checked my 308 loads (LC brass with Nosler 155 gr HPBTs) I had loaded on my Co-Ax and found just .001"-.002" run out. I figger my cast bullet handloads are pretty straight also...
    My Anchor is holding fast!

  11. #11
    I hear the best use of one of those tools it to check each step of your reloading process to find out which ones are ruining your concentricity and then correct it.
    If all is well with the case neck until you seat the bullet and it all goes awry then your seating die is out of spec.
    Use it as a tool to figure out how to make concentric ammo and not need to straighten it out in the end.

  12. #12
    Boolit Grand Master

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    There are several things that happen when you try to correct the loaded rounds concentricity. One it does read centered on the gage but this is a misleading 0 in a way. These adjust by bending the cartridge to "tune" it. So if you bend the cartridge to zero it its longer straight. Also when sprung to zero this can change neck tension slightly Usually lightening it. Bending or springing it can also create out of round necks. Last the bullet can be scored scraped or deformed in the process and cast can be bent or eff shaped also.

    I suggest to set tune your dies to the best possible. Prep tune your brass into the best possible form, Neck turn sort as to wall thickness weight deburr flash holes uniform pockets anneal. Last use dies meant to load quality ammo. Neck bushing dies can improve tension, concentricity and straightness. Neck turning can be a plus if the brass is good at the head and body.

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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