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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Velocity swing in 7mm wsm with IMR 7828ssc
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<blockquote data-quote="elkaholic" data-source="post: 1165954" data-attributes="member: 13833"><p>I think you may have a combination of things there. The 100+ spread you experienced would take a full 2 grains or more of powder to do that (all else equal). Sometimes if you have reached, or rather exceeded, max pressure, your velocity can actually decrease, but that would normally show up as excessive pressure on your case. Several other things have already been mentioned that could also contribute, and there are more. Just leaving a cartridge in a hot chamber for a while before shooting can cause considerable pressure (velocity) increase! This is especially true of powders with high temp sensitivity. It does appear that you have made some progress with the powder charge, but I am still a little suspicious of the chrono being erratic. That 100+ spread is rather telling to me.</p><p>As one poster accurately described earlier though, es does not always have a lot to do with accuracy at 100 yards. I have seen single digit es that would not group and 50' or more spread that would almost shoot one hole. Keep working on your loading including the power charge, neck tension, seating depth, different primer, etc. and see if your es stays consistent. If you continue getting readings as high as you did earlier, I would try another chrono. As far as your coal being much longer; if you are referring to the same charge in a rifle that has been throated, yes, the pressure will be lower. Normally though, seating closer to the lands will raise pressure a little, and some times jamming bullets can raise it considerably. </p><p>I am not suggesting this is your problem, but once you get things figured out, I would still highly recommend that you try some RL26.......Rich</p></blockquote><p></p>
[QUOTE="elkaholic, post: 1165954, member: 13833"] I think you may have a combination of things there. The 100+ spread you experienced would take a full 2 grains or more of powder to do that (all else equal). Sometimes if you have reached, or rather exceeded, max pressure, your velocity can actually decrease, but that would normally show up as excessive pressure on your case. Several other things have already been mentioned that could also contribute, and there are more. Just leaving a cartridge in a hot chamber for a while before shooting can cause considerable pressure (velocity) increase! This is especially true of powders with high temp sensitivity. It does appear that you have made some progress with the powder charge, but I am still a little suspicious of the chrono being erratic. That 100+ spread is rather telling to me. As one poster accurately described earlier though, es does not always have a lot to do with accuracy at 100 yards. I have seen single digit es that would not group and 50' or more spread that would almost shoot one hole. Keep working on your loading including the power charge, neck tension, seating depth, different primer, etc. and see if your es stays consistent. If you continue getting readings as high as you did earlier, I would try another chrono. As far as your coal being much longer; if you are referring to the same charge in a rifle that has been throated, yes, the pressure will be lower. Normally though, seating closer to the lands will raise pressure a little, and some times jamming bullets can raise it considerably. I am not suggesting this is your problem, but once you get things figured out, I would still highly recommend that you try some RL26.......Rich [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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Velocity swing in 7mm wsm with IMR 7828ssc
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