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 !