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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Bullet lift, does it exist?
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<blockquote data-quote="Brown Dog" data-source="post: 177719" data-attributes="member: 1622"><p>Goodgrouper,</p><p></p><p>Yes the thread has wandered a little, my fault. Trouble is, that before you can consider the lift question, you have to establish the bullet's orientation in flight. A misleading bunch of aggressively stated twaddle was posted stating that all bullets maintain their firing orientation throughout their flight. That had to be clarified correctly (well, it didn't have to be, I just chose to <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> ).</p><p></p><p>Bill,</p><p></p><p>I believe most here would accept that bullets are 'wobbly' on shot exit and stabilise over their first 100m or so of flight.</p><p></p><p>And would therefore accept that 'something' is happening to them that causes them to stabilise to point, broadly, into the airflow.</p><p></p><p>The mechanism by which that happens, is the same mechanism by which they are caused to keep themselves broadly pointing on the line of the trajectory through their whole flight.</p><p></p><p>(Obviously the above must be caveated with 'approriately spun' bullets)</p><p></p><p>I thought this one I posted earlier explained in easy terms why a properly spun projectile's nose broadly follows the trajectory :</p><p></p><p></p><p></p><p></p><p>So, </p><p></p><p>As regards 'lift'. </p><p></p><p>Appropriately spun: One of your opening quotes mentioned that Magnus forces arising from the bullet moving into the airflow at a yaw of repose would generate some lift. This is correct. But wildly insignificant...remember that the yaw of repose is a few fractions of a degree.</p><p></p><p>Overstabilised: The projectile will retain its firing attitude. As it begins to fly 'side on' to the airflow, its drag massively increases (obviously they are design optimised to fly nose on). The effect is rather like a space shuttle nose-up re-entry to the atmosphere. The nose-up attitude in that case is clearly to provide a braking effect. I'm not sure I would describe that effect as 'lift'. ...and rather than increasing range, it's always been my understanding that it drastically decreases it.</p><p></p><p>...and to confuse it further...if fully 'side on' and very highly spun, the magnus forces will become far more significant...diverting the round laterally. In extreme examples this can even cause a massively overstabilised projectile to (on a 'plan view' doppler trace) execute a wide slow j-turn.</p></blockquote><p></p>
[QUOTE="Brown Dog, post: 177719, member: 1622"] Goodgrouper, Yes the thread has wandered a little, my fault. Trouble is, that before you can consider the lift question, you have to establish the bullet's orientation in flight. A misleading bunch of aggressively stated twaddle was posted stating that all bullets maintain their firing orientation throughout their flight. That had to be clarified correctly (well, it didn't have to be, I just chose to :) ). Bill, I believe most here would accept that bullets are 'wobbly' on shot exit and stabilise over their first 100m or so of flight. And would therefore accept that 'something' is happening to them that causes them to stabilise to point, broadly, into the airflow. The mechanism by which that happens, is the same mechanism by which they are caused to keep themselves broadly pointing on the line of the trajectory through their whole flight. (Obviously the above must be caveated with 'approriately spun' bullets) I thought this one I posted earlier explained in easy terms why a properly spun projectile's nose broadly follows the trajectory : So, As regards 'lift'. Appropriately spun: One of your opening quotes mentioned that Magnus forces arising from the bullet moving into the airflow at a yaw of repose would generate some lift. This is correct. But wildly insignificant...remember that the yaw of repose is a few fractions of a degree. Overstabilised: The projectile will retain its firing attitude. As it begins to fly 'side on' to the airflow, its drag massively increases (obviously they are design optimised to fly nose on). The effect is rather like a space shuttle nose-up re-entry to the atmosphere. The nose-up attitude in that case is clearly to provide a braking effect. I'm not sure I would describe that effect as 'lift'. ...and rather than increasing range, it's always been my understanding that it drastically decreases it. ...and to confuse it further...if fully 'side on' and very highly spun, the magnus forces will become far more significant...diverting the round laterally. In extreme examples this can even cause a massively overstabilised projectile to (on a 'plan view' doppler trace) execute a wide slow j-turn. [/QUOTE]
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Bullet lift, does it exist?
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