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Thread: Concentricity guage

  1. #16
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    Quote Originally Posted by SPJ View Post
    Yes of course, quite right.. So with this bullet being engraved how does a couple thousand of run out effect trajectory


    Young feller, nobody has mentioned a test and report to affirm one way or another.

  2. #17
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    Well thanks for the compliment , I was just wondering thats all.

  3. #18
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    Quote Originally Posted by Kookie View Post
    Im pretty new to loading 30 BR and found little to no runout in sized case necks, but the seated bullets had .004 - .005 runout. Turned out that there was too much neck clearance with my in-line seating die to get the bullets seated straight. New seater fixed the problem.
    This is more common than most realize.

    Good shootin'. -Al

  4. #19
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    Quote Originally Posted by SPJ View Post
    Yes of course, quite right.. So with this bullet being engraved how does a couple thousand of run out effect trajectory
    The gauge may be, showing misalignment (out of parallel/tilt), as opposed to concentricity (or, a combination thereof). A tilted bullet may result in what the gurus call, "in-bore-yaw", which means that the center-of-gravity will be off-set (eccentric), or, out of balance (the bullet WILL swage & conform the the hole). Thus, unless the misaligned bullets are indexed, one could expect greater dispersion, due to random inertial moment toward the off-set.

    In my early dayz of searching for BR precision, I did experiment with indexing non-turned cases & loaded rounds: indexing the out-of-whack ammo - say, the off-set at 12:00 O'clock - did result smaller group averages than did blind/random and deliberately chambering & firing at all points of the clock. RG

  5. #20
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    Interesting observation, although Im not as seasoned as others Ive had the opposite experience testing at 550 and competing at 600 yards. The term in bore yaw is what I was touching on the other day which again not a Guru by any means find it a tough pill to swallow.
    A possible topic for a good thread.....
    Thx
    J

  6. #21
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    Quote Originally Posted by SPJ View Post
    Interesting observation, although Im not as seasoned as others Ive had the opposite experience testing at 550 and competing at 600 yards. The term in bore yaw is what I was touching on the other day which again not a Guru by any means find it a tough pill to swallow.
    A possible topic for a good thread.....
    Thx
    J
    I believe that "in-bore-yaw" is somewhat of a misnomer - the bullet is not free to yaw & pitch, as is does once spinning free of the bore, rather, it's just eccentrically re-swaged - upon release, "all the bad stuff happens". RG
    Last edited by R.G. Robinett; 11-03-2020 at 12:10 PM.

  7. #22
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    A chambered BR round cant run out much after the bolt is closed.

    We fire our cases with very high pressure and after they are fired they rebound/ shrink back very very little. The fired round brass is within .0005 say of the true chamber size. We size the neck only 3/4 (approx) of the way down the neck and that sized area may only have .002 clearance in the chamber. The real game changer here is that we jam our bullets into the very precise lands/throat area sometimes pushing the bullet back a few thousandths. It is impossible given those close clearances to have a bullet run out .004 to .005 etc etc. There isnt that much clearance anywhere in the chambered round physical clearances. The body fits within .0005 or so. The lower part of the neck that is not sized is very close to dead nuts chamber size. You could possibly seat a bullet crooked but if your seating in the lands that bullet will recenter to its physical clearance AFTER seating hard into the lands. The loaded round concentricity is within the tolerances of the total of the clearances of the chamber/brass fit.
    Wallydog

  8. #23
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    Quote Originally Posted by R.G. Robinett View Post
    The gauge may be, showing misalignment (out of parallel/tilt), as opposed to concentricity (or, a combination thereof). A tilted bullet may result in what the gurus call, "in-bore-yaw", which means that the center-of-gravity will be off-set (eccentric), or, out of balance (the bullet WILL swage & conform the the hole). Thus, unless the misaligned bullets are indexed, one could expect greater dispersion, due to random inertial moment toward the off-set. RG
    As Leon Spinks would say: "Aboulooby!"

  9. #24
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    Cool

    Quote Originally Posted by jim1k View Post
    butch, i think they did a good while back and it didn't mean a rats rear end. But i still use one to check things out if have a problem..... Let me see where i put that thing... Lol...jim
    realy isnt the barrel corect the runout

  10. #25
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    Guys, FWIW, nobody asked about concentricity theory, a simple question for those that have them......which one.

  11. #26
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    Hi Tim,
    I have a NECO and a 21st Century. I like the 21st century better. They do help to identify problem areas in your reloading set up. My problem areas were neck bushings that weren't quite right( run out top and bottom when fitted to a trued mandrel and indicated on the lathe) and a Wilson mic top seater that had been dropped on the concrete about 6 times over the last 10 years.
    Joel

  12. #27
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    Quote Originally Posted by Nader View Post
    Hi Tim,
    I have a NECO and a 21st Century. I like the 21st century better. They do help to identify problem areas in your reloading set up. My problem areas were neck bushings that weren't quite right( run out top and bottom when fitted to a trued mandrel and indicated on the lathe) and a Wilson mic top seater that had been dropped on the concrete about 6 times over the last 10 years.
    Joel
    Thanks buddy

  13. #28
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    Quote Originally Posted by tim View Post
    Guys, FWIW, nobody asked about concentricity theory, a simple question for those that have them......which one.
    I made my own back in the late '90's.

    Be aware that using a stop (that the case head rests against) may cause you to see 'runout' that really isn't there.

    Good shootin'. -Al

  14. #29
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    I once has a large bore balrrel

    that has about a 2" choke in the muzzle end of it. I always figured the reason the rifle shot so well was that 2" of tight choke. Any yawing that might have occurred behind it was quickly righted. It occurs to me folks pay way too little attention the the muzzle end of their CF barrels.

    Pete

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