I have been away for awhile, have been shooting my 1896 carbine in local military matches. Good accuracy with 9.7 grains Unique and 165 grain cowboy cast bullet, very happy with it. Question is: would like to develop load for 30 40 Krag Ruger No. 3, but above load doesn’t work! Where do I start? Would of loved to have same load for both, guess won’t happen. 1896 does inch and under groups at 50 yards.

Cast Bullet Basics For Military Surplus Rifles
By C.E. Harris  Rev. 9-6-93

. . . Do NOT use inert fillers (Dacron or kapok) to take up the excess
empty space in the case.  This was once common practice, but it
raises chamber pressure and under certain conditions contributes
to chamber ringing.  If a particular load will not work well
without a filler, the powder is not suitable for those conditions
of loading.

Four load classifications from Mattern (1932) cover all uses for
the cast bullet military rifle.  I worked up equivalent charges
to obtain the desired velocity ranges with modern powders, which
provide a sound basis for loading cast bullets in any post-1898
military rifle from 7 mm to 8 mm:

1.  125-gr., plainbased "small game/gallery"
         900-1000 f.p.s., 5 grains of Bullseye or equivalent.

2.  150-gr. plainbased "100-yd. target/small game",
         1050-1250 f.p.s., 7 grs. of Bullseye or equivalent.

3.  150-180-gr. gaschecked "200-yard target"
         1500-1600 f.p.s., 16 grs. of #2400 or equivalent.

. . . None of these loads are maximum when used in full-sized rifle
cases such as the .30-40 Krag, .303 British, 7.65 Argentine, 7.7
Jap, 7.62x54R or .30-'06.

. . . For "gaschecked bullets loaded without the gascheck," for cases
like the .303 British, 7.62 NATO, 7.62x54R Russian and .30-'06 I
use 6-7 grains of almost any fast burning pistol powder,
including, but not limited to Bullseye, W-W231, SR-7625, Green
Dot, Red Dot, or 700-X.  I have also had fine results with 8 to 9
grains of medium burning rate pistol or shotgun powders, such as
Unique, PB, Herco, or SR-4756 in any case of .303 British size or
larger.
. . . My favorite load is the most accurate, Mattern's so-called "200-
yard target load".  I expect 10-shot groups at 200 yards, firing
prone rapid with sling to average 4-5". . .

I think I will try the 16 gr-2400, 180 bullet idea

I've read the C. E. Harris article over the last couple years and want to know who is this Mattern he refers to in the original piece.