Author Topic: Tumbling bullets  (Read 1794 times)

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Tumbling bullets
« on: December 04, 2013, 12:19:19 PM »

Offline ID#5

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The Speed of Sound in Air

*The reason the speed of sound in air is important is a rifle bullet is only considered accurate while in supersonic flight, assuming it starts out with a supersonic muzzle velocity

*Maximum effective range for any ammunition is limited to its flight until it begins its transonic flight. Twist rate or Spin is NOT a factor.

*As the bullet transitions from supersonic to transonic to subsonic it gets buffeted by the shockwave in front of it and the bullet can start to yaw and pitch and the heavier tail starts to move around and CAN cause the bullet to lose its consistency/predictability/accuracy. 

*As the bullet is Transonic it is in a period of destabilization.  This period of destabilization can/will cause the bullet to tumble at the very least or it will be deflected off its original flight path, and is therefore unpredictable on its point of impact.

*Supersonic burnout 40M before target in margins for a hit-generally.

The above all comes from the Dean Michaelis .50 Caliber book published in 1999 or 2000.

We just finished the 3rd year of Mile Shoots and alot of shooters have had their bullets go subsonic.  Some times subsonic for 100's of yards
However there have been very few bullet strikes on the targets that have been sideways.

Supersonic range is important but I'm not sure how important.

[##I have had problems with 168grain .308 bullets getting weird between 800 and 1000 yards, but not with any others.  But 168gr SMK bullets are known for this]

my 190SMK and 208AMAX don't seem to be affected by this.

Anyone else have bullets that have gone trans-sonic/sub-sonic without any issues?

How much is that in Mils? - JMack
March 2, 2013

It's completely legal.   The only problem is that it puts you into FR Class (Full Retard), and you might be the only one in the entire country running FR.   Of course, it would set you up for 1st Place in your class, everytime you shoot. 
Big D

Re: Tumbling bullets
« Reply #1 on: December 04, 2013, 12:22:57 PM »

Offline Nealio

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Scharf had a lot of issues with tumbling bullets out of his XD a couple years ago.
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Re: Tumbling bullets
« Reply #2 on: December 04, 2013, 02:05:31 PM »

Offline J Mack

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IMHO, more times than not improper barrel twist is the culprit for bullet destabilization.
Too much twist and the bullet flies nose up and tumbles thru the transonic zone, too little twist and the bullet tumbles into and out of the transonic zone…. 
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