bsteve
From your descriptions I would tell you they are both MMP sabots... I am also inclined to believe the new sabots that you recieved are of the HPH-24 variety and the older ones were of the HPH-12 variety.
The 24's are for tighter barrels:
The big difference between Black HPH12 and HPH24 is HPH24 is .002" smaller
in loaded diameter. Loaded diameter is a sabot with a bullet inserted.
With a .452 diameter bullet the HPH12 is .507-.508" diameter, the HPH24 is .505"-.506" diameter.
If you have a tight loading rifle you may want to choose the HPH24.
This is off the MMP site...
There was a problem with the sabots supplied with the SW's for awhile and now it really escapes me what is was, besides being a bear to load.