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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
A Question for Warren
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<blockquote data-quote="Blaine Fields" data-source="post: 21097" data-attributes="member: 183"><p>Regarding the quality of the air flow around the bullet as it exits: a .308 exiting at 2700 fps is traveling at around Mach 2.3. The exiting gas is traveling at more than Mach 1 faster, correct? If so, wouldn't shockwaves form at the leading edge of the base producing subsonic flow behind and over the surface of the bullet? And wouldn't this flow be essentially laminar? I'm asking because I don't know. I've never seen shadow graphs of a bullet with the base leading, but I would presume that the air would pile up in front of the base and that a stream of moving air would seperate in front of the base, moving around this air mass, pick up speed (venturi effect) and form a standing shockwave at the edge of the base and another where the boat-tail ends and the body of the bullet begins. So I am assuming that the flow on a backwards bullet is essentially laminar all the way around it.</p><p></p><p>I am basing this on shadow graphs of normally oriented bullets, where the flow is apparently laminar until it hits the base where is becomes turbulent. My intuition is that this is what the spotter sees as the bullet wake.</p><p></p><p>At any rate, getting back to the rebated edge, wouldn't the proper way to evaluate this configuration be based upon whether it enhances or is detrimental to the flow properties of the exiting gas around the base of the bullet at the muzzle? Or have I completely missed the boat here?</p></blockquote><p></p>
[QUOTE="Blaine Fields, post: 21097, member: 183"] Regarding the quality of the air flow around the bullet as it exits: a .308 exiting at 2700 fps is traveling at around Mach 2.3. The exiting gas is traveling at more than Mach 1 faster, correct? If so, wouldn't shockwaves form at the leading edge of the base producing subsonic flow behind and over the surface of the bullet? And wouldn't this flow be essentially laminar? I'm asking because I don't know. I've never seen shadow graphs of a bullet with the base leading, but I would presume that the air would pile up in front of the base and that a stream of moving air would seperate in front of the base, moving around this air mass, pick up speed (venturi effect) and form a standing shockwave at the edge of the base and another where the boat-tail ends and the body of the bullet begins. So I am assuming that the flow on a backwards bullet is essentially laminar all the way around it. I am basing this on shadow graphs of normally oriented bullets, where the flow is apparently laminar until it hits the base where is becomes turbulent. My intuition is that this is what the spotter sees as the bullet wake. At any rate, getting back to the rebated edge, wouldn't the proper way to evaluate this configuration be based upon whether it enhances or is detrimental to the flow properties of the exiting gas around the base of the bullet at the muzzle? Or have I completely missed the boat here? [/QUOTE]
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A Question for Warren
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