Although a little faster, I believe 700-X, Green Dot, or AA#5 would be acceptable for most people vs. Unique. AA#5 has a very high bulk density and is good for getting maximum performance from smaller-capacity cases. Probably THE best powder for maximum .38 Super loads.

Fortunately, I think I have about 7 lbs of Unique left so I don't need to worry about running out. Not the best for magnum loads but it will get close to them.