About slugs in RB twists. I made a mould many years ago to cast slugs in my .69. About the lightest was 588gr. and they would actually cloverleaf
at 50yards from a rest. The mould, being adjustable, could cast slugs up to 1,200gr. weight. This rifle has .012" deep rifling rate of 66 in. to a full turn.
The barrel is 31" including the chamber area, so about 29" of actual usable barrel length.
I only used up to 85gr. 2F GOEX with the lightest slugs, due to the increased recoil of these over the normal 482gr. ball weight. At the time I tested these
slugs, my Rb groups were as tight or tighter than the slugs did. Even though the slug weight was only 25% higher than the RB's, the felt recoil seemed
a LOT more. Shooting these slugs actually cracked the stock through the lock bolt, & I repaired it with thin CA model airplane glue. The crack has not reappeared
& I've shot it a large number of times with up to 165gr. and a few with up to 330gr., an accidental double powder charge with 160gr. 3F all with patched round balls.
So - it seems a lot of round ball twists will actually shoot conicals with decent accuracy on paper. We found the .54 and .50ca. TC Maxiballs worked poorly on moose
as they were dreadfully unstable after impact. Perhaps this was only due to the larger size of moose, compared with deer or hogs. My use of patched round balls on
moose, has shown me the surplus nature of slugs in RB rifles. They just aren't needed & on a heavy tough animal, cannot be trusted to maintain their accuracy after
impact. I am talking about poor straight line penetration with slugs in RB twists as the shallow 48" ROT TC's just happene0d to be.
Those Ball-etts you've pictured, might work just fine, Mike, due to their short length.