Something to remember, not all "45cal" bullets are .452. They can vary from .450 to .4525. So, what may work with a 300gr SST (.452) may not work well with a Barnes 290gr TEZ (closer to .4505-.451ish). I have some older Parkers that only run .4505 and new Parkers are .451
I have some Barnes 225gr XPBs that only have a small portion of the bearing surface measuring .451ish. The smallest area is only .450 or a bit less. I can use a much tighter fitting sabot such as the MMP Short or HPH-12 with that bullet.
I can also use a tighter sabot with shorter bullets like the 225gr FTX. The loaded OD is of course larger but the sabot's contact area against the bore is much less than a 300gr bullet in a longer sabot.