You don't need a magnum primer. Winchester's data calls for a Winchester LRP or a magnum primer
What in the world is LRP? I see the acronym as large rifle primer & that's just wrong. Maybe a typo or a brain fart, but dont confuse the OP looking for sound advice.
Winchester's recommendation was for their WLP when they still made the free booklets given away at gunshops. It was, & still is, one of the more brisant of large pistol primers. WW doesn't make a specific magnum pistol primer because they dont need to. Since Hodgdon distributes W-powder these days there is no primer type listed in their current loading data. The charge weight window for 296 is so narrow, it's pretty much a case full of densely packed relatively slow powder or nothing. No reduction is recommended. I would tend to believe the company that makes the stuff... a "hot" pistol primer is needed for consistent ignition under all conditions.
FWIW I've always had best results with WW brass & WLPs in a number of 44s with either W296 or H110 for full power loads with 240-250gr. bullets & a firm roll crimp. Federal 155s worked almost as well & CCI LP mags were 3rd choice. Your lots of components may behave differently. For reduced loads c. 8gr. of Unique or 14gr. of Bluedot has been a reasonably good choice with 240-250gr. cast lead. Almost any LP primer from RP 2 1/2s to WLPs work well for these with little development & I'm sure there are a whole bunch of newer powders that work splendidly.
It's a bad time to get started reloading. Patience, a few long drives, the goodwill of fellow reloaders, & some homework have gotten me most of what I've needed in the past few months.