I have used Blue Dot, a powder with a similar burn rate, for full power loads with 123gr jacketed bullets.  Full power, pressure-wise, but only about 2500fps velocity-wise.  The Krag case is capable of higher velocities with slower powders.  Here's another example, a reduced velocity load with Nosler jacketed 168HPBTs.  Not max by pressure, but I'd guess within "magnum pistol" pressure, wherein the powder burns good.  This was chronographed from a 30" barrel.  Gives you idea of the charge weight you'd be working with 168s, cast or thinly jacketed.  One of my MI friends who shoots his Krag in reduced range (100 yd) matches gets good results.

Oh, now I see 296 is slower than BD!  See what happens when I try to use my memory!  Burn rate is more in line with 4227, which I've also used in cast loads in the 168gr range.

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