You might have something there Sabotloader. I justchecked the"Sabot Experiment" I did withthe Mustang in Sept. `07, usingthe 300 grain GD bulletwith different sabots.

My notes on the targets show the following:

HPH-3P-EZ - Loads very easily, thumb and one finger on ramrod.
Harvester Crush Ribs - Loads easy, one hand steady push.
Harvester Short - Loads firm, two hands steady push.
Harvester Long - Loads firm, two hands steady push.
HPH24 - Loads snug, one long firm push, both hands.
HPH12 - Very tight loading, two hands hard push.

When I shot those two red Smokeless Crush Rib sabots with BH they would have rated about the same as the HPH12s.

I suspect the long flame channel on the Mustang breech plug is the problem. The plug, with a primer inserted, is 1 1/8" from the rear of the primer to the face of the plug, and the plug has a flat face (no dish). Does anyone know how this compares to the length of other plugs?