Oblong bullets

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Wm Cook posted this 2 weeks ago

By now you all know how anal I am and that things that I don’t understand bother me.  Case in point; I don’t understand why bullets don’t drop out of the mold round?  

We’re only talking .0005 and that has no impact on accuracy even though .0005 diameter can make a difference in touching the lands or not touching the lands on a bore rider.

For me this happens with multiple single cavity brass molds from a custom mold maker.  Assume the following

  • #2 or Linotype from Roto-Metal
  • Alloy and mold temperature is managed +/- 10 degrees.
  • There is no indication of finning
  • Molds consistently drop match quality bullets (200 to 230 grain) 70% of the time at +/- .1 and 90+ % of the time +/- .2 grain.
  • And they shoot great.

Beagling other molds can give me >.001 difference and they shoot well so I know this question is kind of silly.

Thanks, Bill Cook.

 

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John Alexander posted this 2 weeks ago

I don't think it's silly I have some of the same unanswered questions.  I wouldn't recommend chemical relief either from those provided by distilling natural products or those provided by big Pharma.

Maybe meditation or yoga might help. Although I tend to go to sleep while trying the former and get motion sickness from some moves of the latter, they work for others.

Others claim that enduring the pain of running marathons give them inner peace,

Good luck enjoying the torments of a cast bullet shooter.

John

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Duane Mellenbruch posted this 2 weeks ago

Perhaps you do not mean oblong, but out of round?  In the second paragraph you mention that the difference in diameter of a bore riding bullet touching the lands or not.  Remember that the lands are in a spiral and will cradle the nose of the bullet, more or less depending upon the twist.  If the nose of the bullet is truly out of round, as long as part of the nose is supported, it will be supported on both sides, and in balance. 

One reason for being slightly out of round is to create "draft" which will allow the casting to drop easier from the mold blocks.  To be specific about your cast bullet, orient the mold seam at 12 and 6.  Mic from 11 to 5, 9 to 3 and 7 to 1.  If the numbers are the same you have a round bullet.  If 9 to 3 is larger than the other two, the cavity is cut deep and might tend to stick in the cavities, (no draft relief in the mold).  If the first and third numbers are not equal, you have an alignment issue that can be corrected.  This is why I believe you mean out of round and not oblong.

 

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Aaron posted this 2 weeks ago

It would seem to me, upon thinking about this, that variance as slight as mentioned above in bullet shape would be negated by the bumping up of the bullet upon shot start or at least along the first few inches of travel down the tube. Bullets do bump up and seal the bore. Heck, the British fired .550" bullets out of 58 caliber rifled muskets and the bullets bumped up even that amount of windage. They were paper wrapped but bump up they did.

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Duane Mellenbruch posted this 2 weeks ago

Refer back to the stated alloy.  British bullets were more likely nearly pure lead, and had black powder propellant.  That would make a difference in obturation from powder ignition.

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Aaron posted this 2 weeks ago

I caught the alloy reference. Even copper jacketed bullets bump up (obturate) when fired. Look at any high speed video of a jacketed bullet leaving the muzzle. You will see propellant gasses preceding the bullet, stopping when the bullet obturates, and continuing upon the bullet exiting the muzzle - now following it. The British bullets were, in fact, pure lead and swaged, not cast. God bless all those little kids rolling cartridges eh?

Even Linotype plasticizes under pressure. It simply isn't all that hard - in the scheme of things. Check out this video of aluminum flowing under pressure. Go to 1:05   

?t=65

 

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