I believe the original intent in the design of the crush rids was to fit bores that the other sabots would not go down with a reasonable amount of effort. I personally try a range of petal thickness of sabots to find the max thickness that will load easy then try all the sabots that have that thickness with each bullet, its the only way I have been able to get consistent results. I also try the in hot weather as the hunting season here usually has some warm days. This is probably why I usually end up with Harvester sabots as the plastic in them stands up to our 100 degree summer weather better, I notice that the guys that live in the colder parts of the country usually use MMP sabots.