I shot quite a few in the .307 Winchester and .30-30AI several years ago. We had a good discussion on the old Beartooth Bullets forum.
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After trying a number of powders I came back to Hodgdon 4198.
Best accuracy, sometimes 5 shot groups under 1 3/4" , were when we put the sabot against the origin of the rifling. I used a mild crimp.
I tried lower velocity loads looking for accuracy the problem was each time I ordered sabots they were a bit different in slots depth and material hardness. There were three distinct sabots back then. E Arthur Brown which were hard and required a higher velocity to open up quickly and leave the bullet. There was another gray sabot that looked similar but with longer slots. This was a medium hard material that seemed to work well at velocities under 2,500 fps.
There is a brown sabot that is made of softer material and works well at 2.500 to 2,350 fps. Above 2,800 fps everyone who shared results reported plastic fouling that was hard to remove.

This was a lot of fun but did not amount to much. In the. 30 caliber leverguns it is hard to beat the 130 grain Speer bullet for varmints and light bodied deer

Slim