I used 5744 for the last loads. Please note for anyone wanting to try this 10 to 15% of smokeless is were you want to be. 10% gets me a clean burn and an additional 100 fps. Your percentage is calculated by using the weight of black powder BY VOLUME and multiplying by 10%. Example 60gr (by volume) x 10% =6grs. Deduct the 6grs from the 60grs and your charge would then be 54grs Bp by volume and 6grs (you can weigh the 6grs) of smokeless powder. Start low and work your way up. I know this sounds simplistic for most of us But the volume measurement of the black powder is important especially in large cases. Just like using Bp loads make sure there is no air space left in the case. Daryl have you ever tried a duplex load in anything as large as a 577x3".