I have a mixture of carbide Sinclair and nitride coated 21st century mandrels. I like the carbide more, they accumulate brass fouling less.
If you're mandrelling new unfired brass, use moly neck lube, or redding graphite lube inside the necks prior to running the mandrel. Brass will gall to the mandrel if not lubed, more so with nitride steel VS carbide, but still to carbide. Lube will eliminate this.
Once brass has been fired a time or two, residual carbon left inside the case neck is usually enough to prevent this from happening anymore. If you're a guy who used stainless media/wet tumbling, you'll want to mandrel before tumbling, as that natural carbon lube will mostly be gone after the wet wash.
