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Long Range Hunting & Shooting
6.5 PRC Powder Charge/Velocity Ladder Test. No Flat Spot
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<blockquote data-quote="gregmark24" data-source="post: 2947765" data-attributes="member: 121785"><p>My buddy and I have been working together on load development for our rifles; his is a 6.5 PRC. In load testing I found a velocity flat spot with my 243, also with good POI, but he has not. </p><p></p><p>Twice now with once-fired Lapua, his powder charged different loads have tracked Gordons Reloading Tool almost exactly. No nodes. The first ladder was 0.010 off the lands with a IMR7828SSC. The second, ladder was with H4831SC, and 0.070 off the lands. He's using Fed 215M primers, producing ~50 ft/sec higher velocities than non-magnum primers (which GRT predicted), and 147 gr ELDM's. At test range of 100 yds, he produced the lowest vertical dispersions with loads 2, 5, and 7 (see chart below); and corresponding velocity SD's of 12.0, 8.9, and 4.6. </p><p></p><p>Questions:</p><p>With 0.6 gr between loads, why were there no discernible velocity flat spots, see graph - average velocities linear with powder charge increments?</p><p>He's got a carbon barrel--does the carbon damp out the harmonics/resonance of the barrel? We'd appreciate any advice you can lend.</p><p></p><p>Velocity Curve vs H4831SC w/ GM215M primers</p><p>[ATTACH=full]511077[/ATTACH]</p><p></p><p>Vertical dispersion - ignore Load 1 and load 10</p><p>[ATTACH=full]511078[/ATTACH]</p></blockquote><p></p>
[QUOTE="gregmark24, post: 2947765, member: 121785"] My buddy and I have been working together on load development for our rifles; his is a 6.5 PRC. In load testing I found a velocity flat spot with my 243, also with good POI, but he has not. Twice now with once-fired Lapua, his powder charged different loads have tracked Gordons Reloading Tool almost exactly. No nodes. The first ladder was 0.010 off the lands with a IMR7828SSC. The second, ladder was with H4831SC, and 0.070 off the lands. He's using Fed 215M primers, producing ~50 ft/sec higher velocities than non-magnum primers (which GRT predicted), and 147 gr ELDM's. At test range of 100 yds, he produced the lowest vertical dispersions with loads 2, 5, and 7 (see chart below); and corresponding velocity SD's of 12.0, 8.9, and 4.6. Questions: With 0.6 gr between loads, why were there no discernible velocity flat spots, see graph - average velocities linear with powder charge increments? He's got a carbon barrel--does the carbon damp out the harmonics/resonance of the barrel? We'd appreciate any advice you can lend. Velocity Curve vs H4831SC w/ GM215M primers [ATTACH type="full" alt="1700019211171.png"]511077[/ATTACH] Vertical dispersion - ignore Load 1 and load 10 [ATTACH type="full" alt="1700019724113.png"]511078[/ATTACH] [/QUOTE]
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6.5 PRC Powder Charge/Velocity Ladder Test. No Flat Spot
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