Alright fellas, I have fooled with this a little bit on my farm and I will drop a couple comments.
1. We are talking about pyrotechnic powder. Black powder, same sulfur, potassium nitrate charcoal mix as black powder for firearms.
2. Not sorted in the same set of screens as the FF, FFF and FFFF system shooters use. Similar, but not samey-same.
3. There are a host of coatings and minor ingredients that can be added to pyrotechnic powder while it is being made to make pretty colors. None of them are good for gun barrels.
4. Black powder, whether pyrotechnic powder or FFg for your .45 Colt is a low explosive. Potentially stricter state laws aside, the federal limit is/was you may posess up to 50# of black powder for personal use at any one time. In many instances (roman candles, rockets that fly) the entire weight of the finished pyrotechnic device counts as black powder. Thus an amatuer pyrotechnician might have 25 pounds of actual black powder tied up in "pyrotechnic devices" that weigh 50 pounds in aggregate, and be at the federal legal possession limit. I do not know the applicable laws in your state.
5. Actual flash powder is a high explosive. It can only be produced, posessed and discharged by ATFE licensees. Period. No exceptions. See #3 above.
6. In practice making homemade pyrotechnic powder that sends bullets out of 45 Colt cases over a choronograph at speeds readily achievable by Goex and Elephant and Swiss is a significant undertaking. Pyrotechnicians need consistent powder, but they aren't racing bullets with each other.