Easy Peasy : Just a different walnut!

Your full length Krag is American black walnut.

Your cut-down rifle stock may be Italian walnut. (IMHO - This stock was reshaped and thinned down in the wrist area by the person who cut it down and sanded it).

Around 1899, Springfield Armory was short on their supply of cured domestic stock wood. A N.Y. lumber supplier, Louis Windmuller and Roelker, eventually supplied 33,000 stocks of Italian walnut.

From my observation, these lighter stocks have a distinctive grain and often 'tiger-stripe'. They will usually have Cartouche dates of 1899, 1900, or 1901. The stocks and hand-guards were often stained dark to fit in with the other rifles in a military unit.

Attached are two pictures of my Italian walnut stock that was stained to darken it, long ago:

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