I believe all brass of recent manufacture for the 500 S&W is made for rifle primers. If you seat a handgun primer and it's too deep, then the case are made for rifle primers. If you seat a rifle primer and you have to really squash it in, then they're made for handgun primers.
Some case had an "R" on the head to show they were made for rifle primers. I don't think Winchester made these cases when they first came out so they're almost for sure for rifle primers.
Also, ignition problems are not caused by Starline brass. It could be a weak hammer spring or a head space problem.