I have not found it difficult at all to create 357 Herrett cases, and I appreciate a few things about it vs the Max that I think make it far nicer. To begin with, Herrett has a beefier rim, and is just bigger brass, and 30-30 is very ubiquitous. It is hard to find 357 Max. Next matter is power. 357 Herrett is simply more powerful, yet can be dowloaded. Another subtle advantage is that it is bottlenecked. This makes it easier to get into a Contender, yet it extracts even better, because the beefier rim makes better engagement on the extractor. Of course, if you want to shoot cast and like chasing the bullet with a card wad and grease cookie, the Max has an advantage. You are pretty limited to 158 grain max if you want to do that in a Herrett.

The key to making Herrett seems to me to be torch annealing the necks before you expand. Here's a rundown of how I do it, and it is one of the easiest and most straightforward conversions I know of.

Take a fired 30-30 case. Hacksaw it off about an 1/8" greater length than 1.750. Anneal it with a torch until the shoulder becomes discolored but stop before it gets too hot to touch, rotate the case as you touch it with the flame. Then lubricate the case and inside of the neck. Expand case and full-length size. Final step, trim to length. I use a Lee lock-stud case trimmer in my electric drill to do this. Chamfer mouth.

Usually when I do this the cases come out so nice that fire forming seems like an unnecessary step. But I will load a starting load first, then neck size case, and from then on us full house loads. The biggest problem is FINDING AA1680!