guys that tells .50ae, what's the trick to getting the crimp right ?

Dad has been working on loading some for my .50 to get cost down but can't quite get the crimp right.

What is not working with your crimp?

The projectiles will spin in the Case.

The crimp has nothing to do with that.  You don't have enough neck tension.  The 50 AE headspaces on the mouth.  You just want to close any belling of the case back up to parallel not a heavy crimp like a revolver case.

What you have is caused by either the case not getting sized enough or your expanding/belling step opening the case back up too far or your crimp is so over done it's causing the bullet to be sized down, making it loose.  Too aggressive of a set up in the expansion die will also cause this as will an oversized expansion mandrill.