BM1455 wrote on Nov 8
th, 2016 at 7:49pm:
. . .I am at 39 grains of IMR 4350 now and I am in the low 1900 ft/ sec already. (1910-1935) That is a little over 100 ft/ sec faster than my first loads which were loaded to 37 grains of that powder. So, a little over 100 ft/ sec more velocity with one full grain of powder. . .
If you gained ~100fps from 37 to 39 grains, that's ~50fps per grain, not 100.
~50fps per grain is what QuickLOAD software predicts -
Cartridge : .30-40 Krag
Bullet : .308, 220, Sierra SPRN 2180
Cartridge O.A.L. L6: 3.089 inch or 78.46 mm
Barrel Length : 30.0 inch or 762.0 mm
Powder : IMR 4350
Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.564% 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
-07.7 84 36.00 1989 1932 28566 4750 87.8 2.033
-05.1 87 37.00 2041 2035 30619 4916 89.1 1.974
-02.6 89 38.00 2093 2141 32819 5077 90.3 1.917
+00.0 92 39.00 2146 2249 35180 5233 91.5 1.862
+02.6 94 40.00 2198 2360 37718 5383 92.6 1.807
+05.1 96 41.00 2251 2474 40443 5528 93.6 1.752 ! Near Maximum !
+07.7 99 42.00 2303 2591 43377 5666 94.5 1.699 ! Near Maximum !