#2344815 - 08/01/08 07:43 AM
Determining Accuracy Nodes with QL and OBT
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Afy
New Member
Registered: 07/26/08
Posts: 3
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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
-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
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 am on the right track? Will this work... any pointers..
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#2347689 - 08/02/08 04:48 PM
Re: Determining Accuracy Nodes with QL and OBT
[Re: Afy]
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Dutch
Campfire Ranger
Registered: 01/28/02
Posts: 2108
Loc: Idaho Falls, ID USA
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I just plugged in your parameters, and 69.2 grains of N160 gives me a barrel time of 1.74 ms. However, your step analysis shows 94 grains for a barrel time of 1.309.........
You can easily get to node 5 (1.22 ms) with any number of slow burners (from RL25, Magpro, MRP, etc). With 95.5 grains of N160 you'll get around 2900, but the other powders can easily beat 3000 fps. HTH, Dutch.
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