According to the website the slug should cast at about 0.728" and weighs just under 1 1/4 oz.
It is a nice looking mould and slug!
With those deep grooves I'd guess the driving bands would swage down quite easily of the slug was oversize. I wonder how well it would knurl? There should be enough band there. My knurler takes my 0.729" as cast slugs up to ~ 0.735"
I'll be looking forward to range reports on this one.
Longbow