well the carcano is a gain twist rifled gun.
but those velocities should be okay.
the 6.5's are notoriuosly difficult to get velocity from [with cast] because of the fast twist rates but a gain twist might actually work in your favor.
however that spread is too far apart, try the filler.
go to 24 grs and a square of the dacron.
also don't be afraid to try a large pistol primer with the lighter loads.
you are well under the 40k that a magnum revolver round will have with those pistol primers.
and is my cut-off point for going to rifle primers.
you could also do some load work with the 2400 powder which might be an easier [non filler load]
alternative.