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.
In life, strive to take the high road....It offers a better field of fire.
"Robo is right" Fuzzball