Here's an short interesting article with a few useful facts:
How to Select the Right Sabot --->>> https://www.chuckhawks.com/select_right_sabot.htm
"Barnes MZ-Expanders come automatically with MMP 50 / 452 Black HPH12 long-petaled sabots in 250 and 300 grain. Here again, while as supplied may load and shoot beautifully for you, if they load unbearably tight, all is not lost. Just substitute MMP 50 / 452 Black HPH-24 sabots. The HPH-24 Black sabots give you a smaller assembled OD of about .002 inches less than the HPH-12 sabots, and that is a whole heck of a lot to a sabot. The example MMP gives is with a .452" bullet: HPH-12 = .507 - .508" assembled OD, HPH-24 = .505 - .506" assembled outside diameter.
Though I'm not a fan of the Hornady SST muzzleloading bullet (Thompson "Shockwave"), if you are shooting the 250 SST or 300 SST, the HPH-12 is generally the choice. If it loads too tight the HPH-24 can solve your problems."
Then the 3petalEZ sabot from MMP is even slightly smaller in diameter.
Having only 3 petals makes it possible to make the petals thinner than having more petals.
But most inline rifles have very shallow rifling without much extra room to hold left over powder fouling.
Here's 2 photo range reports of someone shooting a new Knight Ultra Light Nitride rifle with MMP HPH-24 sabots and 120 grains of Black Horn 209 powder.
2nd report:--->>> https://www.huntingnet.com/forum/bla...ml#post4350495
1st report:--->>> https://www.huntingnet.com/forum/bla...t-nitride.html