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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Lest we forget, the "Short-Fat" technical idea.
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<blockquote data-quote="epoletna" data-source="post: 1571092" data-attributes="member: 87371"><p>Mike:</p><p></p><p>I thought this might be what you were talking about when you said "front ignition". I believe it is a common ignition system in large bore artillery shells.</p><p></p><p>But I think the statement needs further examination:</p><p></p><p>"That powder slug ignites at muzzle release, causing a big ole flash, backfiring down the bore to cause secondary pressure spiking, and slapping the back of released bullets."</p><p></p><p>Lotta parts of that to look at.</p><p></p><p>Is there indeed a "powder slug" that ignites at muzzle release? It sounds like you're describing unburned powder being blown out behind the bullet. With some powders, I suspect that might happen. But there are surely powders that would be consumed entirely in the barrel, so if this were an issue, changing the load would solve it.</p><p></p><p>There is indeed a flash when the bullet exits, no matter what powder is used. Would it be attenuated by igniting the front of the powder column? I would like to see a demonstration of this. I won't say I don't believe it, but given the amount of pressure driving the bullet, I would expect the hot gasses would be nearly the same no matter where the powder load is ignited. In fact I would expect the volume of hot gas that exits immediately behind the bullet would be greater if all the powder is burned before the bullet exits, which I think is what you are suggesting would happen with front ignition. Unburned powder means powder that has not turned into expanded gas, after all.</p><p></p><p>Does that overpressure indeed backfire down the barrel? Seems unlikely to me, as its pressure will not be greater than the pressure inside the barrel.</p><p></p><p>Does it slap the heel of the bullet? Well, it likely continues to push on the back of the bullet, but "slap" it? I cannot see why it would. That implies the bullet has gotten ahead of the gasses pushing it, then they catch up. I'm having a hard time seeing how that would happen. </p><p></p><p>It seems to me the pressure wave would just continue to expand outside the muzzle, dissipating over time. Again, if there is unburned powder in a rear ignition case and not in a front ignition case, there is more more pressure to expand at the muzzle.</p><p></p><p>Of course I know what seems reasonable to a layman might not be how the laws of physics work, but I'm thinking I'd like to see high speed video that demonstrates gas "backfiring" into the barrel or shows the heel of a bullet being "slapped" by the expanding gas. I just have a hard time wrapping my head around that.</p><p></p><p>Companies that produce primers and smokeless powders have had more than a century to examine the burning characteristics of a .30-06 load. I would hope they have optimized the selection of powder and primer to get the most efficiency out of the cartridge. If unburned powder is indeed following the bullet out, a hotter primer or faster burning powder would seem to address that problem. </p><p></p><p>If front ignition offered a perceptible advantage, it would not be hard to fabricate a primer similar to a shotgun primer with an elongated trunk that would move the flash further into the powder column. I would like to hear from the makers of powder and primers about whether they have ever considered or tested such a modification, and what their conclusion was.</p></blockquote><p></p>
[QUOTE="epoletna, post: 1571092, member: 87371"] Mike: I thought this might be what you were talking about when you said "front ignition". I believe it is a common ignition system in large bore artillery shells. But I think the statement needs further examination: "That powder slug ignites at muzzle release, causing a big ole flash, backfiring down the bore to cause secondary pressure spiking, and slapping the back of released bullets." Lotta parts of that to look at. Is there indeed a "powder slug" that ignites at muzzle release? It sounds like you're describing unburned powder being blown out behind the bullet. With some powders, I suspect that might happen. But there are surely powders that would be consumed entirely in the barrel, so if this were an issue, changing the load would solve it. There is indeed a flash when the bullet exits, no matter what powder is used. Would it be attenuated by igniting the front of the powder column? I would like to see a demonstration of this. I won't say I don't believe it, but given the amount of pressure driving the bullet, I would expect the hot gasses would be nearly the same no matter where the powder load is ignited. In fact I would expect the volume of hot gas that exits immediately behind the bullet would be greater if all the powder is burned before the bullet exits, which I think is what you are suggesting would happen with front ignition. Unburned powder means powder that has not turned into expanded gas, after all. Does that overpressure indeed backfire down the barrel? Seems unlikely to me, as its pressure will not be greater than the pressure inside the barrel. Does it slap the heel of the bullet? Well, it likely continues to push on the back of the bullet, but "slap" it? I cannot see why it would. That implies the bullet has gotten ahead of the gasses pushing it, then they catch up. I'm having a hard time seeing how that would happen. It seems to me the pressure wave would just continue to expand outside the muzzle, dissipating over time. Again, if there is unburned powder in a rear ignition case and not in a front ignition case, there is more more pressure to expand at the muzzle. Of course I know what seems reasonable to a layman might not be how the laws of physics work, but I'm thinking I'd like to see high speed video that demonstrates gas "backfiring" into the barrel or shows the heel of a bullet being "slapped" by the expanding gas. I just have a hard time wrapping my head around that. Companies that produce primers and smokeless powders have had more than a century to examine the burning characteristics of a .30-06 load. I would hope they have optimized the selection of powder and primer to get the most efficiency out of the cartridge. If unburned powder is indeed following the bullet out, a hotter primer or faster burning powder would seem to address that problem. If front ignition offered a perceptible advantage, it would not be hard to fabricate a primer similar to a shotgun primer with an elongated trunk that would move the flash further into the powder column. I would like to hear from the makers of powder and primers about whether they have ever considered or tested such a modification, and what their conclusion was. [/QUOTE]
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Lest we forget, the "Short-Fat" technical idea.
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