Hi Otto,
Good question. There's no grape breakdown on the bottle, but I'll suggest to you it is most likely to be predominantly shiraz, although, Stanton and Killeen, and in particular Chris Killeen, winemaker since 1981, has a penchant for this wine style and has been using Portuguese grape varieties more and more over the years. So there could be a possible contribution from Touriga, Bastardo, Alvarelhao, etc (although I wouldn't bet my testicles on it!
) Chris might even use some Durif, as well.