Of course no one is silly enough to actually try 100 grains in their .32's but interestingly enough the Lyman Black Powder Handbook 2nd Ed. shows loads up to 70 grains of both 2Fg and 3Fg Black powder and Pyrodex.
Small bored guns tend to develop rather high pressures with black powder and Pyrodex P goes far higher.
Says the Lyman book, 70 grains of Pyrodex P under a .310 roundball had a breech pressure of 25,600 PSI. That's higher than some modern pistol cartridges.
According to Barlow's Formula for calculating the burst strength of pipes and tubing, that amount of pressure for "Vehement" Pressure pulsations, such as is found when a gun is fired, in a 13/16 inch .32 caliber barrel with a 25,600 PSI breech pressure is unsafe.
Maybe that's why Lymans didn't go higher with their data. (Actually, Lymans book doesn't say the loads they tested are safe. They only give the data that they found in their test barrel.)