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Rifles, Reloading, Optics, Equipment
Reloading
OBT method, barrel length vs velocity
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<blockquote data-quote="Stammster" data-source="post: 1999013" data-attributes="member: 114381"><p>TripodMVR7 - as requested</p><p></p><table style='width: 100%'><tr><td>Gun:</td><td>Browning BAR</td><td></td><td></td></tr><tr><td>Caliber:</td><td>270 Win</td><td></td><td></td></tr><tr><td>Barrel Length:</td><td>20.5" (as measured)</td><td></td><td></td></tr><tr><td>Brass:</td><td>Hornady</td><td></td><td></td></tr><tr><td>Case Capacity:</td><td>70.95 gr (avg) @ 2.532"</td><td></td><td></td></tr><tr><td>Bullet:</td><td>Hornady 130gr SST (27302)</td><td></td><td></td></tr><tr><td>Primer:</td><td>Win WLR (Lot# PGL687G)</td><td></td><td></td></tr><tr><td>Powder:</td><td>Alliant RL26 (Lot# 0819Z013120)</td><td></td><td></td></tr><tr><td>COAL:</td><td>3.230" (seated at canalure)</td><td></td><td></td></tr><tr><td>CBTO:</td><td>2.631" (0.080" jump)</td><td></td><td></td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td>Velocity Recording:</td><td>Magnetospeed Sportster</td><td></td><td></td></tr><tr><td>Temp:</td><td>75F</td><td></td><td></td></tr><tr><td>Charge Weight</td><td>Velocity (3 shot avg - fps)</td><td>Group Size (3 shot - inches) @ 100 yds</td><td>OBT Time (ms calc)</td></tr><tr><td>59.5</td><td>2996</td><td>0.70</td><td>1.089</td></tr><tr><td>60</td><td>3024</td><td>1.20</td><td>1.074</td></tr><tr><td>60.5</td><td>3045</td><td>0.91</td><td>1.060</td></tr><tr><td>61</td><td>3070</td><td>1.98</td><td>1.046</td></tr><tr><td>61.5</td><td>3093</td><td>0.99</td><td>1.030</td></tr><tr><td>62</td><td>3125</td><td>1.28</td><td>1.016</td></tr><tr><td>62.5</td><td>3148</td><td>1.98</td><td>1.002</td></tr><tr><td>63</td><td>3179</td><td>0.80</td><td>0.988</td></tr><tr><td>63.5</td><td>3214</td><td>1.87</td><td>0.975</td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td></td><td></td><td></td><td></td></tr><tr><td>QL Inputs</td><td></td><td></td><td></td></tr><tr><td>Weighting factor:</td><td><div style="text-align: right">0.456</div> </td><td></td><td></td></tr><tr><td>RL 26 Ba (calculated)</td><td><div style="text-align: right">0.365</div> </td><td></td><td></td></tr></table><p></p><p>The above actual data seems to match QL pretty well. This lot of powder has also given the same burn rate in other loads (130 NBT, 145 ELD-X, etc.).</p><p></p><p>By interpolating between the 20" and 21" bbl, I come up with an ideal OBT time of 1.051 ms (node 5) at 3060 fps. 61 gr gave 3070 fps @ 1.046 ms. As you can see, that gave a terrible group size amongst the surrounding charges. 63.5 had a called flyer, otherwise it would have been smaller. All groups were typically triangular shape.</p><p></p><p>Case capacity as measured, 70.95 gr, with a spread between 70.8 and 71.2 gr over qty 10 twice fired (non-resized) brass.</p><p></p><p>All shots were off a rock solid bench, using a led sled. Wind was +/- 10 mph.</p><p>Note: 63.5 charge is just over than SAAMI max 65K psi, but I didn't see any pressure signs. At 63.8 gr I saw some minor signs after the first shot at 3245 fps, so I stopped and pulled those loads. Calculated pressure 68Kpsi.</p></blockquote><p></p>
[QUOTE="Stammster, post: 1999013, member: 114381"] TripodMVR7 - as requested [TABLE] [TR] [TD]Gun:[/TD] [TD]Browning BAR[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Caliber:[/TD] [TD]270 Win[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Barrel Length:[/TD] [TD]20.5" (as measured)[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Brass:[/TD] [TD]Hornady[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Case Capacity:[/TD] [TD]70.95 gr (avg) @ 2.532"[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Bullet:[/TD] [TD]Hornady 130gr SST (27302)[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Primer:[/TD] [TD]Win WLR (Lot# PGL687G)[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Powder:[/TD] [TD]Alliant RL26 (Lot# 0819Z013120)[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]COAL:[/TD] [TD]3.230" (seated at canalure)[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]CBTO:[/TD] [TD]2.631" (0.080" jump)[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD][/TD] [TD][/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Velocity Recording:[/TD] [TD]Magnetospeed Sportster[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Temp:[/TD] [TD]75F[/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Charge Weight[/TD] [TD]Velocity (3 shot avg - fps)[/TD] [TD]Group Size (3 shot - inches) @ 100 yds[/TD] [TD]OBT Time (ms calc)[/TD] [/TR] [TR] [TD]59.5[/TD] [TD]2996[/TD] [TD]0.70[/TD] [TD]1.089[/TD] [/TR] [TR] [TD]60[/TD] [TD]3024[/TD] [TD]1.20[/TD] [TD]1.074[/TD] [/TR] [TR] [TD]60.5[/TD] [TD]3045[/TD] [TD]0.91[/TD] [TD]1.060[/TD] [/TR] [TR] [TD]61[/TD] [TD]3070[/TD] [TD]1.98[/TD] [TD]1.046[/TD] [/TR] [TR] [TD]61.5[/TD] [TD]3093[/TD] [TD]0.99[/TD] [TD]1.030[/TD] [/TR] [TR] [TD]62[/TD] [TD]3125[/TD] [TD]1.28[/TD] [TD]1.016[/TD] [/TR] [TR] [TD]62.5[/TD] [TD]3148[/TD] [TD]1.98[/TD] [TD]1.002[/TD] [/TR] [TR] [TD]63[/TD] [TD]3179[/TD] [TD]0.80[/TD] [TD]0.988[/TD] [/TR] [TR] [TD]63.5[/TD] [TD]3214[/TD] [TD]1.87[/TD] [TD]0.975[/TD] [/TR] [TR] [TD][/TD] [TD][/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD][/TD] [TD][/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]QL Inputs[/TD] [TD][/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]Weighting factor:[/TD] [TD][RIGHT]0.456[/RIGHT][/TD] [TD][/TD] [TD][/TD] [/TR] [TR] [TD]RL 26 Ba (calculated)[/TD] [TD][RIGHT]0.365[/RIGHT][/TD] [TD][/TD] [TD][/TD] [/TR] [/TABLE] The above actual data seems to match QL pretty well. This lot of powder has also given the same burn rate in other loads (130 NBT, 145 ELD-X, etc.). By interpolating between the 20" and 21" bbl, I come up with an ideal OBT time of 1.051 ms (node 5) at 3060 fps. 61 gr gave 3070 fps @ 1.046 ms. As you can see, that gave a terrible group size amongst the surrounding charges. 63.5 had a called flyer, otherwise it would have been smaller. All groups were typically triangular shape. Case capacity as measured, 70.95 gr, with a spread between 70.8 and 71.2 gr over qty 10 twice fired (non-resized) brass. All shots were off a rock solid bench, using a led sled. Wind was +/- 10 mph. Note: 63.5 charge is just over than SAAMI max 65K psi, but I didn't see any pressure signs. At 63.8 gr I saw some minor signs after the first shot at 3245 fps, so I stopped and pulled those loads. Calculated pressure 68Kpsi. [/QUOTE]
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OBT method, barrel length vs velocity
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