[Jim McDougall]

Moving on, I think I have found some interesting perspective on the situation with back powder and the supply to the Mexican army in this time.
Apparently at the time of the 'Texas Revolution', the United States was actually in a pretty much 'business as usual' state as far as commerce in the Gulf of Mexico. This appears to have included supplies to the Mexican army of Santa Anna and through his appointed agents in New Orleans.
The Texians had a small navy of several ships that were patrolling and blockading movement of such supplies in the gulf, and it appears that Yucatan and Maramoros were key port locations for the Mexican trade.

One ship that was captured was Mexican, but owned by Americans (the Pelicano) and apparently had supplies including 300 barrels of powder mingled in with flour and other commodities. Two other American ships were taken also carrying arms, ammunition and powder for the Mexican Army. One ship, a brig from Boston, also had a contract to transport Mexican soldiers to Texas.

While this sounds provocative, it must be remembered that the United States was not at war with Mexico, it was a revolt of the Texians against Mexico. In fact there was considerable uproar of the 'commerce' in the Gulf being disturbed by these nautical situations, and the Texians even accused of piracy!

It would seem that the campaigns in Texas had Santa Anna with a notable shortage of supplies, which apparently included powder. That being the case, perhaps the powder on hand was 'cut' or altered to go farther?
Had the powder being used by Mexico been supplied through New Orleans?, as noted that regular commerce through that major port had been well established.

It would seem that Mexico may have been obtaining powder through New Orleans with Santa Anna through a firm he had business with, and through purchase orders via his worldwide agent for provisions and materials such as ammunition etc.