If not sure what diameter bullets Winchester is currently using for their JSP ammo. At one time they were using .427", then later switched to .425". BUT, I haven't measured any current production. You need to measure the chamber throat diameters of your sixgun, and also the groove diameter of the barrel. Modern reproduction or Colt's production may be running larger...in the .429-.430" range, but I would NOT make the assumption. Presuming the bullets are no larger than these throat and barrel dimensions, you can probably shoot them without running up the pressures.
BTW: Ruger Old Vaqueros, in their early production runs had throats as small as .425" with the barrels in the .429" range. Later, they enlarged the chamber throats to .430", but even they don't know the serial number range where they switched. I shoot HARD CAST bullets that are .430" dia. through the .425" throats with no problems, but if I wanted to shoot jacketed .430" bullets or even .427" JSP, I'd switch cylinders to the .44 Magnums.