I agree. I guess when you first mentioned the uniform pants , I immediately thought that they may belonged to your Grandfather Richard Pittman.
But no matter where the pants came from, it is interesting. Glad Camp Moore is preserving them , & that the 7th Mississippi Website will soon have the photo posted.
I had never heard of the sons of the War of 1812 vets and the Regimental name change. BTW I have ancestors that served in Nixon's 13th Mississippi Territorial Militia during the 1812 / Creek War.

GM