I put a small batch of 78/12/10 powder into the tumbler this morning. I tested a batch of 77/13/10 against my 75/15/10. The tests were 70 grains by volume out of my .50 GPR flinter. The 75% blend went five shots for an average of 1381 fps. The five shot average of the 77% went 1433 fps for an increased speed of 52 fps. I'll let you know what my chrono says about the 78% stuff.