Bob- with such low speeds, perhaps it doesn't take much to spin them, if groove diameter, and soft. I know soft doens't sound right, but soft gives a HARDER hold on the bore all the way out, with pressure behind continually trying to obturate them.

Many loaders will go harder with shallow rifling - we've had 1 1/2 thou grooves with 18" twist, spin .450" 400gr. paper patched pure lead bullets (in a .458" groove dia.) to 1 1/2" accuracy at 100 meters fired with 100gr. of 2F powder.

For 8 years we tried harder and harder cast and hardened cast bullets tryign to get that Sharps to shoot well. Harder bullets made sense to us since jacketed bullets shot so well in it - then a light came on and we tried undersized, paper patched pure lead - instant success.

Of course, the softer alloys are susceptable to stripping or slugging into cylinders, if driven too hard, pressure wise. There is a ballancing act.