Ed,
The powder jaming you heard of was the older style powder measure, and yes it jammed really bad. The newer powder measures say 1995 and later were changed to prevent those problems. I didn't have problems with anyother ball powders just 296 & H-110. I just switched to 2400 and never did get the newer measure.
Come to think of it 296 jammed in my MEC650 .410 loader also. Iguess they are just too fine grained for some measures. 296 and H-110 are the same powder made in the same factory in Fla. as are all the ball powders for both companys,ie H-380=Win.748, H-414=Win 760, HS-6 = Win 540, HS-7 = Win.571. The different powder wts amount to different lots #'s of production used to generate the data.