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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
300 RUM, 200g Accubond, H50BMG
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<blockquote data-quote="Brent" data-source="post: 33164" data-attributes="member: 99"><p>Jon,</p><p> Just meant to say that Retumbo is probably on the fast side for this size of case, in a relative sense that is, and yes, muzzle pressure is raised the slower the powder, and/or the lighter the bullet used. Takes longer to hit peak pressure, bullet is further down the tube by the time pressure drops down and it can affect the bullet on exit if it's high. Much of the same thing using too slow of powder with a light weight bullet that gets down the bore real fast. Generally it has to have a faster powder behind it in order to hit peak pressure soon enough to generate the best speeds, if not muzzle pressure will also be high. I think most of the BR guys try to stay on the faster side of the burn rate, but a lot of it also has to do with better ES numbers too. </p><p></p><p>If you think about it, Retumbo is a pretty slow powder, add to that heavy bullets and they balance out to get good burn in a 26-30" barrel with 90-100gr. The higher the load density, the more peak pressure moves away from the muzzle though, just not as rapidly as it moves toward it going to a slower powder, so the net effect is it moves toward the muzzle. </p><p></p><p>Take H50BMG, it has 102gr at my max load, rise time is slower but load density is much better, the net effect is more muzzle pressure in the same length barrel though. </p><p></p><p>It would be my guess that Retumbo in a 30" barrel would about equal H50BMG in a 34-36" barrel, muzzle pressure wise. </p><p></p><p>I've never used the VV powders yet, but there's a place here in town now that has a pretty good selection for better prices now, so I'll probably add a few to the cabinet sometime soon. I have no idea why, but they recently stopped carrying 8# jugs of Retumbo and 5# jugs of RL25, I was too bummed to even ask why.....</p></blockquote><p></p>
[QUOTE="Brent, post: 33164, member: 99"] Jon, Just meant to say that Retumbo is probably on the fast side for this size of case, in a relative sense that is, and yes, muzzle pressure is raised the slower the powder, and/or the lighter the bullet used. Takes longer to hit peak pressure, bullet is further down the tube by the time pressure drops down and it can affect the bullet on exit if it's high. Much of the same thing using too slow of powder with a light weight bullet that gets down the bore real fast. Generally it has to have a faster powder behind it in order to hit peak pressure soon enough to generate the best speeds, if not muzzle pressure will also be high. I think most of the BR guys try to stay on the faster side of the burn rate, but a lot of it also has to do with better ES numbers too. If you think about it, Retumbo is a pretty slow powder, add to that heavy bullets and they balance out to get good burn in a 26-30" barrel with 90-100gr. The higher the load density, the more peak pressure moves away from the muzzle though, just not as rapidly as it moves toward it going to a slower powder, so the net effect is it moves toward the muzzle. Take H50BMG, it has 102gr at my max load, rise time is slower but load density is much better, the net effect is more muzzle pressure in the same length barrel though. It would be my guess that Retumbo in a 30" barrel would about equal H50BMG in a 34-36" barrel, muzzle pressure wise. I've never used the VV powders yet, but there's a place here in town now that has a pretty good selection for better prices now, so I'll probably add a few to the cabinet sometime soon. I have no idea why, but they recently stopped carrying 8# jugs of Retumbo and 5# jugs of RL25, I was too bummed to even ask why..... [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
300 RUM, 200g Accubond, H50BMG
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