W-296 is a powder that likes to fill 95-100% of the available case capacity (with the bullet seated). There used to be "work up" data published, but Winchester found some problems. I would follow the manufacturer's recommendations! Ask your gunsmith if he will replace your firearm and pay your medical expenses if his information is incorrect.
I have it on good authority that W-296 and H-110 are the EXACT same thing. They are now made/marketed by the same outfit. This may be true. I'm still not going to use data for one powder, with another powder.