I have loaded for both Herretts, some years ago.
There was some BS involved in their creation and promotion - when announced it was claimed that the parent cartridges had too much capacity for pistol barrels, and would never shoot accurately.
The .357 Herrett barrel I owned had a rough chamber and never would shoot accurately. Sold. Don't think Dad ever shot his, much.
Some years later one of the originators wrote of how nicely accurate .30-30's Contender pistol barrels could be, apparently forgetting what he had written ten years beforehand, or else learning something new.
The Herretts are good cartridges, and if you find a good barrel they should work fine, but they won't do anything a .30-30 or .35 Remington won't do.