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Rifles, Reloading, Optics, Equipment
Reloading
QL v3.6 just arrived and its conflicting info
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<blockquote data-quote="Pdvdh" data-source="post: 395384" data-attributes="member: 4191"><p>Fitch, have you ever tried it? I mean other than on the QL software? </p><p></p><p>Below is a string of MV data from my 300 Win Mag with the bullet seated from 0.040" off the lands to 0.070" off the lands. Seating depth is increased in 0.005" increments. Two rounds were fired and chronographed per seating depth. MV drops with increased seating depth and reduced case capacity. So, the theory may sound great, but it's not reflected in measured MVs. </p><p></p><p>Primer = CCI 250</p><p>Powder = H1000</p><p>Bullet = 180 grain Aluminum-tipped, Rebated Base Boattail</p><p></p><p>I'm familiar with the natural gas law, and the Pressure/Volume relationship. But the natural gas law doesn't account for changing volume as the bullet moves down the bore, and the increased friction as the bullet enters the rifling.</p><p></p><p>I'm also familiar with my chronographs and the results many others experience and report. [The first recorded MV at 0.060" off the lands (<em>3035?</em>) is in italics, because it's a questionable value. I run two chronos concurrently in tandem and the difference in velocities over the two chronos was skewed for that shot, meaning one of the chronos recorded a flawed value.]</p><p></p><p>(0.040") 3024</p><p>(0.040") 3021 Avg=<strong>3022.5</strong></p><p></p><p>(0.045") 3028</p><p>(0.045") 3010 Avg=<strong>3019</strong></p><p></p><p>(0.050") 3021</p><p>(0.050") 3022 Avg=<strong>3021.5</strong></p><p></p><p>(0.055") 3017</p><p>(0.055") 3015 Avg=<strong>3016</strong></p><p></p><p>(0.060") <em>3035?</em></p><p>(0.060") 3017 Avg=<strong><em>3026?</em></strong></p><p></p><p>(0.065") 3013</p><p>(0.065") 2990 Avg=<strong>3001.5</strong></p><p></p><p>(0.070") 2999</p><p>(0.070") 3001 Avg=<strong>3000</strong></p><p></p><p>You're aware of the freebore added to some of the Weatherby Magnum cartridge chambers? It allows additional powder to be placed in the cases, resulting in increased MV, for cartridges with bullets seated to the same depth in the cases - compared to chambers lacking the freebore.</p><p></p><p>Kirby Allen has modified the throat design on some of his chamberings, allowing increased powder charges and MV, by allowing the bullets to transition into the rifling with less friction. He used a more tapered throat design.</p><p></p><p>I'm aware of increased pressures created by jamming the bullet into the rifling. </p><p></p><p>Now, with the bullets seated to already clear the lands, my guess is that giving the bullets additional jump into the lands by increasing seating depth reduces pressure and MV by reducing the friction (and associated pressure jump) as the bullet enters the rifling. </p><p></p><p>I have read many experiences contrary to your statements, and the test shooter for the HATs bullets has repeated my experience of reduced MV with increased seating depths - over and over again. Very predictable in his rifles.</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 395384, member: 4191"] Fitch, have you ever tried it? I mean other than on the QL software? Below is a string of MV data from my 300 Win Mag with the bullet seated from 0.040" off the lands to 0.070" off the lands. Seating depth is increased in 0.005" increments. Two rounds were fired and chronographed per seating depth. MV drops with increased seating depth and reduced case capacity. So, the theory may sound great, but it's not reflected in measured MVs. Primer = CCI 250 Powder = H1000 Bullet = 180 grain Aluminum-tipped, Rebated Base Boattail I'm familiar with the natural gas law, and the Pressure/Volume relationship. But the natural gas law doesn't account for changing volume as the bullet moves down the bore, and the increased friction as the bullet enters the rifling. I'm also familiar with my chronographs and the results many others experience and report. [The first recorded MV at 0.060" off the lands ([I]3035?[/I]) is in italics, because it's a questionable value. I run two chronos concurrently in tandem and the difference in velocities over the two chronos was skewed for that shot, meaning one of the chronos recorded a flawed value.] (0.040") 3024 (0.040") 3021 Avg=[B]3022.5[/B] (0.045") 3028 (0.045") 3010 Avg=[B]3019[/B] (0.050") 3021 (0.050") 3022 Avg=[B]3021.5[/B] (0.055") 3017 (0.055") 3015 Avg=[B]3016[/B] (0.060") [I]3035?[/I] (0.060") 3017 Avg=[B][I]3026?[/I][/B] (0.065") 3013 (0.065") 2990 Avg=[B]3001.5[/B] (0.070") 2999 (0.070") 3001 Avg=[B]3000[/B] You're aware of the freebore added to some of the Weatherby Magnum cartridge chambers? It allows additional powder to be placed in the cases, resulting in increased MV, for cartridges with bullets seated to the same depth in the cases - compared to chambers lacking the freebore. Kirby Allen has modified the throat design on some of his chamberings, allowing increased powder charges and MV, by allowing the bullets to transition into the rifling with less friction. He used a more tapered throat design. I'm aware of increased pressures created by jamming the bullet into the rifling. Now, with the bullets seated to already clear the lands, my guess is that giving the bullets additional jump into the lands by increasing seating depth reduces pressure and MV by reducing the friction (and associated pressure jump) as the bullet enters the rifling. I have read many experiences contrary to your statements, and the test shooter for the HATs bullets has repeated my experience of reduced MV with increased seating depths - over and over again. Very predictable in his rifles. [/QUOTE]
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QL v3.6 just arrived and its conflicting info
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