I need a tighter loading sabot

[Underclocked]

I have some Lehigh 250 XP's that I need to shoot up. This is for my Vortek LDR which using the Thors measures a .501. I tried the harvester smooth black and it was loose. That has been my go to with the PT golds.  
I have Knight Blues, orange MMP, red cr, yellow cr, and a few MMP 12 & 24. Before I start ramming them down to find out I figured I would ask the group.

 

[exMember]

possibly try the red crush rib sabot, those are for the savages with the larger bores.

 

[Blacksheep]

Try a bag of the Hornady black sabots (mmp ?) with Hornady 452 bullet they mike at .505-.506 so with a 451 bullet  I would think .504 -505 which ought to work .  I use them in my 1/48 sidelocks and they are tight.