That will work fine (please don't do it with an original Colt, though). But if you do it that way, you use a smaller drill to go all the way through. That way if the plunger gets stuck at some time, it can be driven out from the front (after the hammer and hand are removed). Also cut a groove in the plunger tail and crimp the front spring coil into it, so the two pieces are one unit and easier to handle (and find on the floor).
Jim
Jim