Just curious as to how effective duplex shot charges are (like combining #4's and #6's)?

Wouldn't the different velocities of the differently sized shot mess things up?

The different sized shot are contain in a shotcup, this shot cup holds the shot till they begin exiting the barrel so at the beginning they are all moving at the same speed. By the time the lighter pieces have started to drop in velocity significantly more than the larger pieces the pattern will have opened up enough that it won't matter.

I've never seen a Duplex load, either factory or handloaded, that patterned well.

DC

You need to mix the shot 60/40 by WEIGHT not volume with the 60% being the larger size. You also need to jump at least one size to obtain a good duplex IE: 7.5/5 or 6/4. If you attempt to duplex by loading the shot sizes separately into the hull, as DMC said, they are not going to pattern well.

This is just out of curiousity again but would those loads only be good for stationary targets (turkeys etc), or could you use them with wingshooting? I was just thinking that the different velocities would really make patterning a mess when you're trying to shoot something that's moving.

You have to tune the load just like any other load but I've used them wing shooting since around '84. I'll drop you an email later today with some details.
Mark