If you have to use a sub, T7 is about the only one with any power, that doesn't have perchlorates in it's mixture, according to the late Bill Knight.

Perchlorates make the fouling exceedingly corrosive, as-in Pyrodex.

Bill noted that Hodgdon used the same MSDS sheet for T-7 as with Pyrodex, but in his chemical analysis of it, he said T-7 did not have any of that chlorate substance in it's mixture, whereas Pyrodex was 17% per volume, perchlorates.
That's the bad shit. It's of of the detonating compounds made WW1 era corrosive primers, corrosive.

The load I showed, did not increase the original velocity of the .50/70 round, likely due to the use of GOEX 1F for the 60gr. load of black powder. It did, however achieve a vel. of 1,200fps, which is close to normal for that round with the 450gr. bullet.