But remember, when that Ordnance Manual was published, there were millions of rounds of smoothbore ammunition in store. They were not going to take the time to break up any cartidges just to remove part of the powder charge. They only broke up ammunition when it became unserviceable. Even in the 1862 manual, 110 grs. was still specified as the charge.
And musket powder was a little coarser than ffg, somewhere around the equivalent of fg and a half or fg. I wouldn't be fooling around with a 110 gr. charge of fffg, that's for sure. My .69 shoots best with 80 grs. of ffg and a bare ball.