It won't be very even... I mean, a LED PR base bulb will allow for a wider range of adjustment before having 'black holes' than the incand bulb will, but you will never see an edge to edge floodlight with a polished Mag reflector, I don't believe.
There are other things you can do... you can sputter the reflector which gives an even larger hotpost, but then you start to lose throw which isn't really a problem if you are after a floodbeam. But it is sill 'throwy' rather than a true flood light such as a SureFire L4.