Re: win 748 in the .220 swift
From The Reloading Manual for Rifle and Handgun by Nick Harvey (2nd edition) .
Starting load for 50gn is 36gns of 748 for 3640 FPS , maximum of 40 gns for 3900 . For 55gn try 35gns for starting load and 38.5gn maximum for about 3830 FPS . Work up to maximum loads with caution as I couldn't get near these maximums in my Sako.
Personally found 748 faster than optimum for the Swift . Suggest you try H4350 , work up to 43 - 44 gns with a 50gn projectile . Try 760 if you want to use ball powder .
According to my manual VV-N160 (max 46gn) gives top velocities with those bullet weights if that's what you want .