Wild guess
They used the MMP short black which has a large loaded OD with a .451-.452 bullet. Roughly around .508+
Using the .445 bullet loaded OD is much smaller (obviously) but it still fits the short sabot very well. The bullet may set too deeply in a longer sabot and catch the jag on loading.
Last edited by Gm54-120; 02-03-2016 at 07:34 AM.