Well it says so right on Knights website too...so there.
https://www.knightrifles.com/product/ma ... er-sabots/
And MMP calls the 54x50 purple.
http://mmpsabots.com/store/purple-sabot/
So this aint on me. :yeah:
BTW anyone considering a 52 should not be concerned about bullets. 458s are perfectly matched to the 52cals performance limitations. Them silver sabots handle 130gr of BH209 with a 325gr bullet like nothing. You are getting close to the 450Marlin performance area with that load. The 475 325gr XTP does just fine in the 52x475s too but bullets like the Speer 275gr are really short in that sabot. If you want to shoot bullets under 300gr you will need to look at monos like the Lehighs/Bloodlines or Hornady 458 250gr GMX bullet. The 458 GMX/Monoflex is very similar in size to the 325gr FTX.
I even shot the Barnes 300gr 458SOCOM bullet in mine. It shot really well for a boattail in a standard sabot. That bullet is all kinds of nasty on deer at ML speeds.