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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Understanding cartridge efficiency
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<blockquote data-quote="corsair4360" data-source="post: 1914950" data-attributes="member: 63474"><p>I have analyzed this and came up with a term "overbore index" which is the capacity of the case in grains divided by the area of the bore in inches. For 7mm cartridges here is a bit of the analysis:</p><table style='width: 100%'><tr><td>Name</td><td>Bullet</td><td>Case length</td><td>Rim</td><td>Base</td><td>Shoulder</td><td>Neck</td><td>OAL</td><td>Case Cap</td><td>Overbore Index</td></tr><tr><td>7mm-08 Remington</td><td>0.284</td><td><div style="text-align: right">2.035</div> </td><td><div style="text-align: right">0.473</div> </td><td><div style="text-align: right">0.470</div> </td><td><div style="text-align: right">0.454</div> </td><td><div style="text-align: right">0.315</div> </td><td><div style="text-align: right">2.800</div> </td><td><div style="text-align: right">47.8</div> </td><td><div style="text-align: right">755</div> </td></tr><tr><td>7×57mm Mauser</td><td>0.284</td><td><div style="text-align: right">2.244</div> </td><td><div style="text-align: right">0.473</div> </td><td><div style="text-align: right">0.472</div> </td><td><div style="text-align: right">0.430</div> </td><td><div style="text-align: right">0.324</div> </td><td><div style="text-align: right">3.060</div> </td><td><div style="text-align: right">54.3</div> </td><td><div style="text-align: right">857</div> </td></tr><tr><td>.284 Winchester</td><td>0.284</td><td><div style="text-align: right">2.170</div> </td><td><div style="text-align: right">0.473</div> </td><td><div style="text-align: right">0.500</div> </td><td><div style="text-align: right">0.475</div> </td><td><div style="text-align: right">0.320</div> </td><td><div style="text-align: right">2.800</div> </td><td><div style="text-align: right">66.0</div> </td><td><div style="text-align: right">1042</div> </td></tr><tr><td>.280 Remington</td><td>0.284</td><td><div style="text-align: right">2.540</div> </td><td><div style="text-align: right">0.473</div> </td><td><div style="text-align: right">0.470</div> </td><td><div style="text-align: right">0.441</div> </td><td><div style="text-align: right">0.315</div> </td><td><div style="text-align: right">3.330</div> </td><td><div style="text-align: right">68.0</div> </td><td><div style="text-align: right">1073</div> </td></tr><tr><td>7mm Remington SAUM</td><td>0.284</td><td><div style="text-align: right">2.035</div> </td><td><div style="text-align: right">0.534</div> </td><td><div style="text-align: right">0.550</div> </td><td><div style="text-align: right">0.534</div> </td><td><div style="text-align: right">0.320</div> </td><td><div style="text-align: right">2.825</div> </td><td><div style="text-align: right">69.2</div> </td><td><div style="text-align: right">1092</div> </td></tr><tr><td>.280 Ross </td><td>0.284</td><td><div style="text-align: right">2.590</div> </td><td><div style="text-align: right">0.556</div> </td><td><div style="text-align: right">0.534</div> </td><td><div style="text-align: right">0.404</div> </td><td><div style="text-align: right">0.317</div> </td><td><div style="text-align: right">3.500</div> </td><td><div style="text-align: right">76.0</div> </td><td><div style="text-align: right">1200</div> </td></tr><tr><td>7mm WSM</td><td>0.284</td><td>2.1</td><td>0.535</td><td>0.555</td><td>0.538</td><td>0.321</td><td><div style="text-align: right">2.850</div> </td><td>76.8</td><td><div style="text-align: right">1212</div> </td></tr><tr><td>7mm Remington Magnum</td><td>0.284</td><td><div style="text-align: right">2.500</div> </td><td><div style="text-align: right">0.532</div> </td><td><div style="text-align: right">0.512</div> </td><td><div style="text-align: right">0.491</div> </td><td><div style="text-align: right">0.315</div> </td><td><div style="text-align: right">3.290</div> </td><td><div style="text-align: right">81.4</div> </td><td><div style="text-align: right">1285</div> </td></tr><tr><td>7mm Weatherby Magnum</td><td>0.284</td><td><div style="text-align: right">2.550</div> </td><td><div style="text-align: right">0.530</div> </td><td><div style="text-align: right">0.511</div> </td><td><div style="text-align: right">0.490</div> </td><td><div style="text-align: right">0.312</div> </td><td><div style="text-align: right">3.250</div> </td><td><div style="text-align: right">85.0</div> </td><td><div style="text-align: right">1342</div> </td></tr><tr><td>7mm STW</td><td>0.284</td><td><div style="text-align: right">2.850</div> </td><td><div style="text-align: right">0.513</div> </td><td><div style="text-align: right">0.532</div> </td><td><div style="text-align: right">0.487</div> </td><td><div style="text-align: right">0.315</div> </td><td><div style="text-align: right">3.600</div> </td><td><div style="text-align: right">92.6</div> </td><td><div style="text-align: right">1462</div> </td></tr><tr><td>7mm RUM</td><td>0.284</td><td><div style="text-align: right">2.850</div> </td><td><div style="text-align: right">0.534</div> </td><td><div style="text-align: right">0.550</div> </td><td><div style="text-align: right">0.525</div> </td><td><div style="text-align: right">0.322</div> </td><td><div style="text-align: right">3.650</div> </td><td><div style="text-align: right">108.1</div> </td><td><div style="text-align: right">1706</div> </td></tr></table><p>This may help some, infuriate others, and cause others to contemplate...</p></blockquote><p></p>
[QUOTE="corsair4360, post: 1914950, member: 63474"] I have analyzed this and came up with a term "overbore index" which is the capacity of the case in grains divided by the area of the bore in inches. For 7mm cartridges here is a bit of the analysis: [TABLE] [TR] [TD]Name[/TD] [TD]Bullet[/TD] [TD]Case length[/TD] [TD]Rim[/TD] [TD]Base[/TD] [TD]Shoulder[/TD] [TD]Neck[/TD] [TD]OAL[/TD] [TD]Case Cap[/TD] [TD]Overbore Index[/TD] [/TR] [TR] [TD]7mm-08 Remington[/TD] [TD]0.284[/TD] [TD][RIGHT]2.035[/RIGHT][/TD] [TD][RIGHT]0.473[/RIGHT][/TD] [TD][RIGHT]0.470[/RIGHT][/TD] [TD][RIGHT]0.454[/RIGHT][/TD] [TD][RIGHT]0.315[/RIGHT][/TD] [TD][RIGHT]2.800[/RIGHT][/TD] [TD][RIGHT]47.8[/RIGHT][/TD] [TD][RIGHT]755[/RIGHT][/TD] [/TR] [TR] [TD]7×57mm Mauser[/TD] [TD]0.284[/TD] [TD][RIGHT]2.244[/RIGHT][/TD] [TD][RIGHT]0.473[/RIGHT][/TD] [TD][RIGHT]0.472[/RIGHT][/TD] [TD][RIGHT]0.430[/RIGHT][/TD] [TD][RIGHT]0.324[/RIGHT][/TD] [TD][RIGHT]3.060[/RIGHT][/TD] [TD][RIGHT]54.3[/RIGHT][/TD] [TD][RIGHT]857[/RIGHT][/TD] [/TR] [TR] [TD].284 Winchester[/TD] [TD]0.284[/TD] [TD][RIGHT]2.170[/RIGHT][/TD] [TD][RIGHT]0.473[/RIGHT][/TD] [TD][RIGHT]0.500[/RIGHT][/TD] [TD][RIGHT]0.475[/RIGHT][/TD] [TD][RIGHT]0.320[/RIGHT][/TD] [TD][RIGHT]2.800[/RIGHT][/TD] [TD][RIGHT]66.0[/RIGHT][/TD] [TD][RIGHT]1042[/RIGHT][/TD] [/TR] [TR] [TD].280 Remington[/TD] [TD]0.284[/TD] [TD][RIGHT]2.540[/RIGHT][/TD] [TD][RIGHT]0.473[/RIGHT][/TD] [TD][RIGHT]0.470[/RIGHT][/TD] [TD][RIGHT]0.441[/RIGHT][/TD] [TD][RIGHT]0.315[/RIGHT][/TD] [TD][RIGHT]3.330[/RIGHT][/TD] [TD][RIGHT]68.0[/RIGHT][/TD] [TD][RIGHT]1073[/RIGHT][/TD] [/TR] [TR] [TD]7mm Remington SAUM[/TD] [TD]0.284[/TD] [TD][RIGHT]2.035[/RIGHT][/TD] [TD][RIGHT]0.534[/RIGHT][/TD] [TD][RIGHT]0.550[/RIGHT][/TD] [TD][RIGHT]0.534[/RIGHT][/TD] [TD][RIGHT]0.320[/RIGHT][/TD] [TD][RIGHT]2.825[/RIGHT][/TD] [TD][RIGHT]69.2[/RIGHT][/TD] [TD][RIGHT]1092[/RIGHT][/TD] [/TR] [TR] [TD].280 Ross [/TD] [TD]0.284[/TD] [TD][RIGHT]2.590[/RIGHT][/TD] [TD][RIGHT]0.556[/RIGHT][/TD] [TD][RIGHT]0.534[/RIGHT][/TD] [TD][RIGHT]0.404[/RIGHT][/TD] [TD][RIGHT]0.317[/RIGHT][/TD] [TD][RIGHT]3.500[/RIGHT][/TD] [TD][RIGHT]76.0[/RIGHT][/TD] [TD][RIGHT]1200[/RIGHT][/TD] [/TR] [TR] [TD]7mm WSM[/TD] [TD]0.284[/TD] [TD]2.1[/TD] [TD]0.535[/TD] [TD]0.555[/TD] [TD]0.538[/TD] [TD]0.321[/TD] [TD][RIGHT]2.850[/RIGHT][/TD] [TD]76.8[/TD] [TD][RIGHT]1212[/RIGHT][/TD] [/TR] [TR] [TD]7mm Remington Magnum[/TD] [TD]0.284[/TD] [TD][RIGHT]2.500[/RIGHT][/TD] [TD][RIGHT]0.532[/RIGHT][/TD] [TD][RIGHT]0.512[/RIGHT][/TD] [TD][RIGHT]0.491[/RIGHT][/TD] [TD][RIGHT]0.315[/RIGHT][/TD] [TD][RIGHT]3.290[/RIGHT][/TD] [TD][RIGHT]81.4[/RIGHT][/TD] [TD][RIGHT]1285[/RIGHT][/TD] [/TR] [TR] [TD]7mm Weatherby Magnum[/TD] [TD]0.284[/TD] [TD][RIGHT]2.550[/RIGHT][/TD] [TD][RIGHT]0.530[/RIGHT][/TD] [TD][RIGHT]0.511[/RIGHT][/TD] [TD][RIGHT]0.490[/RIGHT][/TD] [TD][RIGHT]0.312[/RIGHT][/TD] [TD][RIGHT]3.250[/RIGHT][/TD] [TD][RIGHT]85.0[/RIGHT][/TD] [TD][RIGHT]1342[/RIGHT][/TD] [/TR] [TR] [TD]7mm STW[/TD] [TD]0.284[/TD] [TD][RIGHT]2.850[/RIGHT][/TD] [TD][RIGHT]0.513[/RIGHT][/TD] [TD][RIGHT]0.532[/RIGHT][/TD] [TD][RIGHT]0.487[/RIGHT][/TD] [TD][RIGHT]0.315[/RIGHT][/TD] [TD][RIGHT]3.600[/RIGHT][/TD] [TD][RIGHT]92.6[/RIGHT][/TD] [TD][RIGHT]1462[/RIGHT][/TD] [/TR] [TR] [TD]7mm RUM[/TD] [TD]0.284[/TD] [TD][RIGHT]2.850[/RIGHT][/TD] [TD][RIGHT]0.534[/RIGHT][/TD] [TD][RIGHT]0.550[/RIGHT][/TD] [TD][RIGHT]0.525[/RIGHT][/TD] [TD][RIGHT]0.322[/RIGHT][/TD] [TD][RIGHT]3.650[/RIGHT][/TD] [TD][RIGHT]108.1[/RIGHT][/TD] [TD][RIGHT]1706[/RIGHT][/TD] [/TR] [/TABLE] This may help some, infuriate others, and cause others to contemplate... [/QUOTE]
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Understanding cartridge efficiency
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