Also let me take this opportunity to welcome you to the forum... Nice to have you here.
One thing I do not understand about the Black Mag3 container, what top are you supposed to use to be able to pour that out of the container it comes in? I tried a Goex cap, and too small, and the Pyrodex is too large. Perhaps there is an in between one I do not have in my collection. I was going to shoot some the other day, but did not have a free horn to fill with the powder. Normally I throw a pour cap on the pound of powder and then load into the measure right out of that. The only time I take a horn is hunting.
Another thing is when you get that powder, make sure to shake the snot out of that pound of powder. I could hear chunks in two of the pounds I shook. I finally got the one I have which seems in gain form to say the least.