OBT and Load Node


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Afy
August 1, 2008, 10:37 AM
Trying to figure out the most accurate predicted load using QL and Optimal barrel time...

Cartridge : .300 Win. Mag.(@)
Bullet : .308, 168, Sierra HPBT MatchK 2200
Useable Case Capaci: 82.988 grain H2O = 5.388 cm³
Cartridge O.A.L. L6: 3.340 inch = 84.84 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Vihtavuori N160

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-20.0 75 55.36 2209 1820 24802 8054 82.7 1.670
-18.0 77 56.74 2262 1909 26308 8344 84.0 1.633
-16.0 79 58.13 2316 2000 27901 8632 85.3 1.596
-14.0 81 59.51 2370 2094 29590 8917 86.6 1.560
-12.0 83 60.90 2424 2191 31380 9198 87.8 1.524
-10.0 85 62.28 2478 2290 33276 9474 89.0 1.489
-08.0 87 63.66 2532 2392 35286 9745 90.1 1.456
-06.0 89 65.05 2587 2496 37411 10009 91.2 1.422
-04.0 91 66.43 2641 2602 39642 10266 92.2 1.383
-02.0 92 67.82 2696 2711 41991 10516 93.2 1.345
+00.0 94 69.20 2751 2822 44478 10756 94.1 1.309
+02.0 96 70.58 2805 2936 47113 10987 95.0 1.274
+04.0 98 71.97 2860 3052 49906 11207 95.8 1.240
+06.0 100 73.35 2915 3169 52867 11417 96.5 1.207
+08.0 102 74.74 2970 3289 56008 11614 97.2 1.175 ! Near Maximum !
+10.0 104 76.12 3024 3412 59343 11798 97.8 1.144 ! Near Maximum !

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 94 69.20 2897 3130 52400 10992 98.7 1.214
Data for burning rate decreased by 10% relative to nominal value:
-Ba 94 69.20 2570 2464 36730 10068 86.3 1.430

69.2 is no where near the max load...
Hwever given a 24 inch barrel... It gives me a barrel time of 1.309 miliseconds which is about as close to 3.308 OBT as I can get. And a +/- 10% puts me right in the ball parks of the next OBT nodes...

Please tell me I havent gone nuts? Will this work...

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Afy
August 1, 2008, 10:38 AM
I have gone raving nuts.... am in the wrong section. My apologies...:banghead::banghead::banghead:

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