ReloaderFred
Member
Walksalong, I believe your conclusion begs the question: if it a diameter problem with Dillon's die, then why doesn't it effect all the cases?
Most of my re-resized cases emerged from the re-resizing (using Dillon's die) without any belting. If it were a diameter problem, wouldn't all the brass have been effected?
Dies are manufactured to +/- SAAMI specs. If the die is made to minimum SAAMI specs, and your chambers are maximum SAAMI specs, they're both "in specification", but there's a lot of difference between the two sizes. It's called "spec stacking". On top of that, the Dillon die probably has a rather sharp edge at the mouth, whereas the RCBS die has a radius at the mouth of the carbide insert. A sharp edge will cut, or shave, brass, while the radius edge will iron it out.
Like I said before, I'd simplify my life and use the die that works, and send the offending die back for a refund.
Hope this helps.
Fred