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Posted: 11/13/2011 6:36:22 AM EDT
| Hey guys. Got a box of hornadys superformance 75 grain bthp ammo, I am shooting it out of a rra 20".with a 1/9 twist. Its rated at 2970 fps. Could it be that this round is a little fast for my rifle. Did not group great. I reload alot of the 75 gr bthp in lc with 23.0gr of accurate 2460. Groups much better but I dont have a chrono so I am not sure what my hand loads are steaming at. I am guessing slower because when I brought the hand loads up to 23.5 and 24 gr, they began to get inaccurate. Thanks in advance. |
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This data has been pretty close for me using other Accurate powders.
ETA: I forgot to correct the case capacity the first time, this data closely matches my test loads with Accurate powders. Cartridge : 5.56 mm NATO - 5.56 x 45 mm Bullet : .224, 75, Hornady BTHP M 2279 Useable Case Capaci: 26.172 grain H2O = 1.699 cm³ Cartridge O.A.L. L6: 2.260 inch = 57.40 mm Barrel Length : 20.0 inch = 508.0 mm Powder : Accurate 2460 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 71 18.40 2108 740 25479 6452 87.7 1.439 -18.0 73 18.86 2160 777 27098 6660 89.0 1.403 -16.0 75 19.32 2212 815 28821 6863 90.2 1.368 -14.0 76 19.78 2264 854 30655 7061 91.3 1.333 -12.0 78 20.24 2316 893 32606 7252 92.4 1.299 -10.0 80 20.70 2368 934 34682 7437 93.4 1.267 -08.0 82 21.16 2420 976 36891 7614 94.4 1.235 -06.0 84 21.62 2472 1018 39241 7783 95.3 1.199 -04.0 85 22.08 2524 1061 41744 7944 96.1 1.165 -02.0 87 22.54 2576 1105 44408 8095 96.8 1.132 +00.0 89 23.00 2628 1150 47247 8236 97.5 1.100 +02.0 91 23.46 2679 1195 50273 8366 98.1 1.069 +04.0 92 23.92 2730 1242 53502 8485 98.6 1.039 ! Near Maximum ! +06.0 94 24.38 2781 1288 56949 8592 99.0 1.011 ! Near Maximum ! +08.0 96 24.84 2832 1336 60632 8687 99.4 0.983 ! Near Maximum ! +10.0 98 25.30 2883 1384 64573 8769 99.6 0.956 !DANGEROUS LOAD-DO NOT USE! 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 89 23.00 2758 1267 56748 8117 100.0 1.015 ! Near Maximum ! Data for burning rate decreased by 10% relative to nominal value: -Ba 89 23.00 2455 1003 38113 7942 90.9 1.213 |
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