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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Custom rifle
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<blockquote data-quote="cjuve" data-source="post: 2426740" data-attributes="member: 31341"><p>All of these groups were shot during load development not final loads. </p><p></p><p>Looking at the POI from surrounding charge weights I have come to the conclusion that what you are seeing is a result of bad harmonic timing. If you look at the targets at 600 yds (orange dot is about 2") you will see that the 95 grain load strung vertical to over 5" and had an overall higher POI than that of the faster 95.3 grain load which had zero vertical dispersion. The lower charge load was exiting the muzzle just after the barrel had started its upward movement from being stationary at the bottom of its harmonic cycle. The higher charge load exited the muzzle at the bottom of the harmonic cycle while it was at its most stationary point. When you get on the wrong side of this cycle interesting things happen which don't always show up at close range. </p><p></p><p>The timing of the barrel cycle is really evident when you shoot long range ladders, it is part of the reason that you can have a series of loads that impact within the same vertical even when they differ in charge weight by up to 1.5 grains. I have found that a properly tuned load can hold the same POI even when shooting .5 gr or more difference in charge weights. This is also why you can a load with higher than normal es/sd still print good groups at long range.</p></blockquote><p></p>
[QUOTE="cjuve, post: 2426740, member: 31341"] All of these groups were shot during load development not final loads. Looking at the POI from surrounding charge weights I have come to the conclusion that what you are seeing is a result of bad harmonic timing. If you look at the targets at 600 yds (orange dot is about 2") you will see that the 95 grain load strung vertical to over 5" and had an overall higher POI than that of the faster 95.3 grain load which had zero vertical dispersion. The lower charge load was exiting the muzzle just after the barrel had started its upward movement from being stationary at the bottom of its harmonic cycle. The higher charge load exited the muzzle at the bottom of the harmonic cycle while it was at its most stationary point. When you get on the wrong side of this cycle interesting things happen which don't always show up at close range. The timing of the barrel cycle is really evident when you shoot long range ladders, it is part of the reason that you can have a series of loads that impact within the same vertical even when they differ in charge weight by up to 1.5 grains. I have found that a properly tuned load can hold the same POI even when shooting .5 gr or more difference in charge weights. This is also why you can a load with higher than normal es/sd still print good groups at long range. [/QUOTE]
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