The bullets look good.

I am curious about the shape of the Lyman/type slug. It is similar to the shape of a waisted air rifle pellet. The air rifle pellets are not stable in the transonic zone of velocity. I do not know if this is a factor of the rate of twist in these rifles or not, but they are happiest in the sub 980fps range.

Are the standard Lyman slugs 'happy' with supersonic speeds?

What groups sizes have been made or are expected from rifled barrels?

Perhaps a standard-shaped slug would be best?