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Rifles, Reloading, Optics, Equipment
Reloading
What is “powder bridging”?
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<blockquote data-quote="azsugarbear" data-source="post: 1679623" data-attributes="member: 4809"><p>Powder bridging most often occurs in cartridges that have these three things in common: 1) stick powder; 2) "overbore" cartridges (as in powder charge to bore diameter) and finally; 3) usually an improved case. Most cases are based off of military designs that have gently sloping shoulders for better feeding and extraction of a round. When a case is "improved" it usually involves moving the shoulder forward and giving the shoulder a more acute angle. This improvement allows more powder capacity in the case. The improved shoulder cuts down on the amount of stretching that occurs in the neck/shoulder area, thus improving case life. Some also feel that it also helps mitigate throat erosion. While I cannot address the idea of less throat erosion, I can opine as to the case life of improved cartridge brass. I used to own a 277 Allen Mag. It was based on the 338 Lapua case and burned over 100 grains while propelling a 195 gr. bullet at about 3,150 fps. I had more than 12 firings on nearly all my Lapua brass before any signs of thinning brass became apparent in the wall close to the case head.</p><p></p><p>The downside of this type of cartridge design is that it was prone to powder bridging. Due to the acute angle of the shoulder, along with a large amount of powder trying to get out that .277 bore, bridging became a potential nightmare. Pressures could/would spike quickly and become very dangerous. You couldn't predict when it would occur as it was not a consistent. But the potential for extreme spiking was enough to convince a shooter to not go anywhere near that cliff. I ran only US 869 ball powder in mine.</p></blockquote><p></p>
[QUOTE="azsugarbear, post: 1679623, member: 4809"] Powder bridging most often occurs in cartridges that have these three things in common: 1) stick powder; 2) "overbore" cartridges (as in powder charge to bore diameter) and finally; 3) usually an improved case. Most cases are based off of military designs that have gently sloping shoulders for better feeding and extraction of a round. When a case is "improved" it usually involves moving the shoulder forward and giving the shoulder a more acute angle. This improvement allows more powder capacity in the case. The improved shoulder cuts down on the amount of stretching that occurs in the neck/shoulder area, thus improving case life. Some also feel that it also helps mitigate throat erosion. While I cannot address the idea of less throat erosion, I can opine as to the case life of improved cartridge brass. I used to own a 277 Allen Mag. It was based on the 338 Lapua case and burned over 100 grains while propelling a 195 gr. bullet at about 3,150 fps. I had more than 12 firings on nearly all my Lapua brass before any signs of thinning brass became apparent in the wall close to the case head. The downside of this type of cartridge design is that it was prone to powder bridging. Due to the acute angle of the shoulder, along with a large amount of powder trying to get out that .277 bore, bridging became a potential nightmare. Pressures could/would spike quickly and become very dangerous. You couldn't predict when it would occur as it was not a consistent. But the potential for extreme spiking was enough to convince a shooter to not go anywhere near that cliff. I ran only US 869 ball powder in mine. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
What is “powder bridging”?
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