.357 Carbine w/1:20 twist

[PineyCreek22]

I have a .357 carbine with a 1:20 twist barrel. I want to shoot cast lead bullets.  First time out it grouped about 3-1/2" @100 yards with 160 gr. cast bullets and 8.7gr Accurate #5 powder.  I have been told that a lighter bullet might do better.  What would be a better powder and bullet weight for this little carbine.  Piney Creek

[tacklebury]

I have a .357 carbine with a 1:20 twist barrel. I want to shoot cast lead bullets.  First time out it grouped about 3-1/2" @100 yards with 160 gr. cast bullets and 8.7gr Accurate #5 powder.  I have been told that a lighter bullet might do better.  What would be a better powder and bullet weight for this little carbine.  Piney Creek

Try a 125 gr. and some Unique.  I'd guess about 6 gr.  My 1:16 twist throws 158's and 180's quite well though.