I ran a bit of a comparison between fmj-swc slugs and hard cast slugs from my 45 acp. The fmj-swcs are Mag-Tech fmjs. The jacket seems thick enough. The cast bullet is the old Lyman 454423, the plain based Keith design for the 45 Auto Rim. The test medium was a cross cut section of a big telephone pole. I shot lengthwise into the cross cut section with 3 loadings, all over 6.5 grains of Unique.
The slugs were the 230 gn fmj rn-ball, the 230 gn fmj-swc and the 238 gn (245 actual weight) Lyman 454423; estimated velocity for each loading was 877'/sec as per my Lyman 43rd Edition.
They all penetrated the same distance, about 6". The fmj rn-ball slug more readily followed the grain of the wood (Cedar) and began to yaw at about the 5" mark, finally ending at 6" with a 45 degree yaw. The fmj-swc and the 454423 also penetrated about 6" but drove straight on until stopping. Neither bullet was deformed and could have been re-used.
I think that if used for hunting the fmj-swc slug would perform the same as a hard cast swc. jmtcw.