Assuming you are talking about the .427 old bullet diameter with the .429 of the XTP. I looked in some of my old Winchester catalogs, I have them back to the 20's and they show a .429 jacketed bullet in their loaded ammo of 200gr. From a 60 year old Lyman manual #38, they also show a jacketed bullet but not the diameter or brand in 200 grs using 2400. The data says For Rifles ONLY. Peaked out they have 23.5grs 2400 under their bullet which they say is at 1700'ps. Factory jacketed ammo was at 1330'ps per my catalogs. I don't know how hard you want to push that Winchester. I don't push mine at all. I quit using jacketed ammo in all of the oldies as barrel life is shorter on the old steel with jacketed bullets. So it's kinda "It's yer rifle, do what ya wanna do" kinda thing. I'd probably be happy some where around 1200'ps with an XTP. FWIW, Hornady recommends velocities of no more than 1500'ps with that bullet.
