Can't help but feel the lack of straight penetration being likely due to poorer constructed solids rather than the 14",and 15" ROTs normal for the calibre these days.
Seems to me the 9.3's having 14"ROTs shoot SD bullets of over .300 just fine.
Now, with the older normal slower twists in .458 cal. of 18" to 22", I can understand where a faster twist (14" or 15") might be advisable, but not faster than that in such a larger calibre.